Environmental history of China

, the cradle of Chinese agriculture Before the development of agriculture, people hunted for a living or gathered food from forests, grasslands, or wetlands, with minimal impact on the environment. Hunter-gatherers may have used fire to clear underbrush in forests to allow new grass to grow, attracting deer herds for easier hunting, but the forests themselves remained. About 10,000 years ago, with the expansion of agriculture, forests began to give way to farmland. Between 5000 and 3000 BCE, during the Yangshao culture period, people in the central Yellow River basin became heavily dependent on domesticated plants and animals. Increasing reliance on domesticated species such as cattle, sheep, and horses allowed exploitation of previously difficult drylands. Farmers initially cleared land by burning grass and used stone hoes and spades to turn the soil. As agriculture developed on the Loess Plateau, increasing use of fire and tillage led to soil erosion, increasing the sediment load carried by the Yellow River, which in turn raised the riverbed and banks, expanding the flood-prone area of the North China Plain. Settled agriculture required clearing forests for farmland. Increased food supply from farming led to population growth, necessitating more land clearance. Yangshao people gradually developed methods to clear forests and open farmland. Initially, clearing a plot near the village sufficed, but over time, with technological advances and population pressure, more forests were destroyed. Using stone axes to fell trees was time-consuming and laborious, while burning entire forests was uncontrollable and dangerous. People employed a method of girdling individual trees—stripping a ring of bark from the trunk to block water and nutrients from the roots, allowing the tree to wither naturally. This allowed precise removal of specified numbers of trees. Villagers cleared most forests around settlements for firewood and cultivation, and wetlands also decreased. In the Yangtze River basin and Loess Plateau, two agricultural systems supported growing populations, leaving less pasture for livestock. However, Neolithic farmers never altered the environment on a large scale. By 2000 BCE, there were probably about 1,000 villages in northern China, each generally housing only a few hundred people and occupying small areas, leaving ample space for wild plants and animals. == Shang dynasty ==

living in North China during the Shang dynasty The Shang dynasty controlled vast territory and had a dense population. Its northwestern boundary roughly coincided with the modern 20-inch (50 cm) isohyet. West and north of this rainfall line were grasslands and deserts unsuitable for cultivation. Shang civilization's territory extended from deciduous broadleaf oak forests southward to the mixed deciduous and subtropical forests of the Yangtze River basin. Major crops included two types of millet, rice, and mulberry. They began transforming the North China Plain into farmland, but large forested areas still provided various game. Tigers, elephants, and rhinoceroses lived in the forests. Most of northern China remained dense forest, with only small patches of farmland. Approximately 4–5 million people lived on the North China Plain, with grain yields of about one shi per mu, implying that roughly to of oak forest had been cleared. Cleared land was usually located within forests to facilitate hunting. Around major cities such as Anyang, the surrounding countryside was largely cleared for farmland. Shang people cleared forests tree by tree rather than burning entire tracts, to avoid danger and waste fuel. Oracle bone inscriptions also record forest burning, often related to hunting. Burning could clear native vegetation for farming; fires could drive wild animals from forests for easier capture; and burning could drive away birds and beasts, providing safety for cultivators and protecting crops from trampling. The Shang established walled cities and entered the Bronze Age. Bronze casting required burning large quantities of wood for mining, smelting, and casting, greatly affecting the surrounding environment. When forests were exhausted, the mines were abandoned; after copper and tin reached the capital's foundries, even more wood was needed for refining. The Shang center was located between the flood-prone plains and the relatively well-drained area near the Taihang Mountains. Capitals frequently relocated because the Shang practiced shifting cultivation; after several years, soil fertility declined and yields dropped. At that time, people lacked good farming tools and could only use ash from burned vegetation as fertilizer. Without plowing with spades or plows, they relied only on the surface layer of fertility. Within a few years, the soil was exhausted, yields declined, and farmers had to migrate to open new fields. This was the long-term fallow system of primitive agriculture. The Shang had vast hunting grounds west and south of Mount Tai. Shang people hunted not only gentle game such as deer, foxes, wolves, and badgers but also large animals such as elephants, tigers, and rhinoceroses. In the densely populated lowlands of Henan, farmland and domestic grazing animals gradually occupied the habitats of large mammals, and human herds gradually replaced native animal populations. The expansion of domestic herds reduced land available for wild animals, leading to the extinction of aurochs and wild horses, and making the region the first in East Asia where large animals permanently disappeared. By the late 2nd millennium BCE, large wild mammals had largely vanished from the North China lowlands and survived only in sparsely populated surrounding mountainous areas. == Zhou dynasty ==

Western Zhou flowing through the Western Zhou royal domain The core area of the Western Zhou was the Wei River valley, where dryland agriculture first developed in China. Loess soil was easy to cultivate and could be planted year after year. In the early Western Zhou, large areas of uncultivated land still existed on the North China Plain and in the Wei River valley. Forest clearance expanded eastward, northeastward, and northwestward from the Shang core on the North China Plain. The eastern Yellow River alluvial plain was flat and densely forested. Because the Yellow River flooded periodically, the area was originally unsuitable for farming or building cities, so settlements were built on higher ground north and south of the river channel. The Zhou used stone or wooden plows to open land, pulled by human labor or oxen. Loess soil was highly susceptible to erosion, so the Zhou built ridges in fields to reduce soil loss. Feudal states attached great importance to forest protection, with strict forestry laws. Because population was sparse and land abundant, the incentive for people to destroy forests was not strong. This was equivalent to indirect prohibition through taxation. Forestry laws prevented reckless felling, and mountain and forest access for harvesting was seasonal. Entering mountains to harvest beyond the permitted period or felling trees that should not be cut was called "stealing wood" and subject to punishment. Some forests were completely closed, with even harsher penalties for violations. The southern state of Chu had more forests than the central states. By the 6th century BCE, forests had become very scarce in the coastal area of northeastern Shandong. Around 500 BCE, iron tools began to appear and were soon used in agriculture and for making iron plows. The first to use iron farming tools were the state of Wu. Warring States period , who noted the denuded Ox Mountain By the 4th century BCE, iron-smelting technology had spread widely in the Yangtze River basin, and northern feudal states began mass-producing iron tools. Iron foundries required large amounts of wood to make charcoal for smelting ore; wood was scarcer than ore, so large-scale deforestation and environmental destruction became common. In densely populated areas, all woodland around cities had disappeared, and farmland of the various feudal states adjoined one another. Due to excessive timber cutting, areas near the capitals of large states became bare Ox Mountain. By around 300 BCE, people had thoroughly altered the land of North China. Mencius criticized the felling of Ox Mountain's forests. To increase revenue, rulers of the various states opened wastelands and forests for farmland to recruit farmers, attract migrants, and expand the agricultural population. During the Warring States period, digging irrigation canals was common practice. For example, the state of Qin built the Zhengguo Canal, diverting water from the Jing River into the Luo River over 126 km to irrigate and flush salts from saline-alkali land between the Jing and Luo, turning wasteland into fertile fields. This completed agricultural reclamation in the Guanzhong region. The Warring States competed to control forests, wetlands, and minerals, appointing officials to manage and tax them to strengthen state power. The made the benefits of mountains, forests, rivers, and marshes the exclusive property of the ruler and established officials to collect taxes on them. The state took control of forests and marshes that had once been communal resources, thereby exercising far greater control over the natural ecology within its territory than ever before. In the eastern part of the Guanzhong Basin, soil erosion began to intensify due to agricultural expansion. In the densely populated areas of the North China Plain, pastures within farming regions became increasingly scarce; the growing population encroached upon the living space of herbivorous livestock such as cattle and sheep, leaving only animals like dogs, pigs, and chickens—which could survive in human settlements—behind . The Zhou people developed wetlands along riverbanks and in poorly drained areas, causing the deer and water deer—two species that inhabited these wetlands—to eventually disappear from the Yellow River basin. As farmland expanded, deer herds in the lowlands dwindled, and most of the remaining land was used for grazing cattle, sheep, and goats. By the end of the Warring States period, large wild animals in the North China Plain were few and far between, and aurochs, wild horses, and wild water buffalo eventually became extinct. From then on, large animals in the North China Plain were found only in the . The three northern states of Qin, Zhao, and Yan expanded northward, occupying semi-arid farming and pastoral zones, then advancing further into nomadic territories. They drove nomadic peoples from their pastures and built the Great Wall to defend against their attacks. The Central Plains states needed resources from the grasslands, especially horses for cavalry and pasture for grazing. Facing incursions from the Central Plains, the Xiongnu formed alliances to resist. During the Warring States period, people gradually realized that nature's bounty was not limitless and needed timely maintenance to prevent resource depletion and food shortages. Mencius emphasized land management, advocating soil and water conservation measures and urging the royal family and wealthy to live moderately to avoid exhausting resources. The Guanzi, compiled around 250 BCE, pointed out that natural resources were finite and that successful rulers should strictly limit resource exploitation to prevent exhaustion. However, due to the pressures of war, resource protection policies rarely succeeded in the various states. == Qin and Han dynasties ==

Central Plains The agricultural empire model created by the Qin and Han became the way most Chinese dynasties organized the state for the next two thousand years. The Qin government undertook massive projects. To supply timber for building palaces in Xianyang and the Great Wall, forests in the Inner Mongolian Plateau and nearby mountains were destroyed. Most of the Hexi Corridor was originally grassland oasis with abundant water and grass, and the Qilian Mountains had extensive forests. The tuntian areas were located on the edge of the desert, where forests were already sparse. Tuntian activities did not expand windbreak forests but instead first cut down trees. Sometimes excessive water use in upstream tuntian areas affected downstream water supply, causing rivers to change course. Original oases became desolate and disappeared, eventually turning into desert. Examples include in Gaotai County and Suoyang City in Anxi, both harmed by artificial river course changes, with land gradually desertifying. The wild grass vegetation on the desert edge originally served as a natural barrier against wind and sand. Crops, however, left large gaps between plants, making it difficult to block wind and sand. Moreover, crops were harvested in autumn, leaving the ground completely bare for about half the year, precisely when wind and sand were strongest. Tuntian farmland had no vegetation to block wind and sand, leading to desert encroachment. Even more unfortunately, when the Han dynasty's national strength weakened and the policy of relocating civilians to strengthen the border was halted, people withdrew from the tuntian areas. The former tuntian zones became large areas of abandoned land with long-term bare ground. Without even the weak wind and sand blocking effect of crops, strong winds carried large amounts of sand particles deep inland, causing the desert to expand year by year. == Wei, Jin, Northern and Southern dynasties ==

North The disaster of Yongjia in 311 caused a massive population decline in the north, with large numbers of Han people migrating south to the Yangtze River basin to escape chaos. Northern China experienced wave after wave of nomadic invasions, while many Han people retreated to mountain forts (wubao). During the 4th–5th centuries, there were hundreds of forts in northern China. With sparse population and large areas of abandoned land, both Han and non-Han rulers tried to resettle farmers on the fields. Invaders tried to capture Han farmers and confine them to secure zones they controlled, concentrating them near the conquerors' capitals. After people were taken away, the occupied land was abandoned. Mark Elvin noted that due to the southward movement of pastoralists, grasslands and forests in North China regenerated, and Yellow River breaches decreased to once every 50 years or less. Robert Marks, however, argues that northern forests did not regenerate or recover because most had already been felled during the Han, leaving almost no seed sources. Troops constantly marched through the land, making it difficult even for shrubs to grow. Nomadic peoples brought grazing animals, turning former Han farmland into pastures for millions of horses and sheep. Sheep grazed plants bare, inhibiting the regeneration of trees and shrubs. The range of tigers shrank dramatically as their habitats and food sources were destroyed, leading them to begin attacking humans and eating people. South During the chaos of the Yongjia Disaster, hundreds of thousands to a million Han people fled south to the Yangtze River basin and even further to the South China Sea (Guangzhou). Han people drove out southern natives and settled there. Southern land was densely covered with rivers and lakes, with dense forests covering hills and mountains, originally unsuitable for agriculture. The Yangtze Delta and Hangzhou Bay areas were still uninhabitable. (During the Warring States, the state of Yue settled on higher hills, slopes, or alluvial fans rather than in swamps and low river valleys.) The lowlands were filled with brackish water, with fluctuating water areas and levels. People on higher plains could farm, while those in low plains and coastal sandy areas engaged in salt production and fishing. At that time, aristocratic families from the lower Yangtze began investing large amounts of labor and resources to gradually transform southern land into rice paddies, replacing forests and swamps with farmland. To ensure rice growth, the Han needed to level the land thoroughly before cultivation, build dikes around fields, and install sluice gates for drainage and irrigation. The Han were able to drain and tame low-lying land. The entire Yangtze River basin's river valleys were transformed, and beyond rice paddies, flood-control dikes were built, massively altering the south's wet environment. In the lower Yangtze, new settlements were located on lower plains and river valleys suitable for rice cultivation, with dense mountain forests between fields inhabited by non-Han "Man," "Lao," "Li," and "Xi" peoples whose lifestyles had not yet been assimilated by the Han. During the Eastern Jin, powerful families seized mountains, lakes, rivers, and marshes. Great clans illegally occupied mountains and marshes. In 336, the Eastern Jin issued a strict prohibition against occupying mountains and marshes, known as the "Renchen Regulation." However, it was difficult to enforce effectively, resulting in powerful families violating the law by occupying mountains and sealing waters, while the government was powerless to punish them. Common people had no such privileges, creating extreme unfairness. Because it was difficult to strictly prohibit powerful families from occupying mountains and sealing waters, during the reign of Emperor Xiaowu of Liu Song (453–464), the regulation was changed. While reaffirming that occupying mountains and marshes was an encroachment on state-owned land, it recognized existing private property as a fait accompli. This allowed private individuals to legally own mountains and marshes, but with limits based on official rank. From then on, mountain and forest property rights in the Southern Dynasties operated under a dual-track system of state and private ownership. Private individuals could legally acquire mountain and forest property rights. Open access to mountains and forests became the norm, with strict closures being special cases. With private ownership of mountains and forests permitted, in suitable areas people transformed occupied mountain land into terraces for water storage and rice planting; in unsuitable mountainous areas, they turned them into millet fields, continuing the early slash-and-burn fallow system. West In the 4th century, Lao tribes appeared in northern Sichuan. They lived in lowlands along rivers and practiced shifting cultivation, burning part of the forest and planting taro and millet in the ashes until the soil's nutrients were exhausted after a few years, then moving to the next forest patch. The Lao were forced by the Han to leave the lowlands; some retreated to the mountains, while most chose to adapt to Han life. In the highlands of Sichuan, the Yi lived in fortified villages on mountain tops. To provide pasture for their livestock, they burned forests in the mountains. Later, as the Yi population grew and they moved into lowland forests, they still practiced slash-and-burn agriculture. When competing with the Han for land, the Yi would retreat to their mountain-top fortresses. == Sui and Tang dynasties ==

North During the Tang, forests in the north had been largely felled. During the Sui and Tang, the Zhongnan Mountains could generally only supply the capital's daily firewood needs. Even so, after the mid-Tang, even firewood began to fall short, and larger construction timber had to be obtained from prefectures such as Lan and . To protect Chang'an from soil erosion from surrounding hills and to raise awareness of natural environmental protection, the Tang issued laws. Perhaps influenced by Buddhist precepts against killing, the Tang also enacted laws restricting killing and hunting seasons. People recognized the serious consequences of forest degradation but could do little to save China's forests. To supply fuel, large numbers of trees planted along Chang'an's main roads were felled. During the mid-Tang, all accessible pine trees in present-day Shandong, Shanxi (Taihang Mountains), and Shaanxi had been felled, mainly to burn pine smoke for ink production. As the riverbed continued to rise, dikes were built along both banks of the Yellow River during the Tang, and the soil for raising the dikes was dug from nearby areas, increasing the height difference between nearby land and the river. Seepage turned many low-lying areas into swamps, and because salts in the water could not drain away, a belt about wide along the river became uncultivable saline-alkali land. oasis near Dunhuang During the Tang, the Hexi Corridor became a major transportation route and part of the Silk Road. As population increased, suitable land was colonized and turned into farmland, resulting in desert expansion and shrinkage of the Dunhuang oasis. The desertification process was irreversible. During the Tang, Buddhist monasteries also altered the natural environment. Monasteries were generally built in uncultivated mountainous or hilly areas or other unused land. During the Sui, there were over 4,000 large monasteries distributed across north and south China, each overseeing large numbers of farmers and servants who cultivated land for them. Monasteries were also surrounded by trees, gardens, and pastures. They cleared mountainous land for farmland, pastures, orchards, and timber forests, transforming original forests into various productive arbor or shrub forests, such as tea gardens and orchards (orange trees were most common), and planted construction materials such as timber and bamboo. Jiangnan In the Yangtze Delta region, Han rice cultivation was mostly limited to higher elevations. By the 9th century, the Han had invented new water control techniques and began effectively reclaiming low-lying areas. At that time, the main problem facing farmers was flooding. Annual monsoon rains caused major floods in the Yangtze, overflowing riverbanks across the middle and lower reaches into plains, lakes, and marshlands. The Han solved this with polder fields (weitian)—completely enclosing farmland with earthen dikes to prevent floodwater entry. Sluice gates in the dikes allowed drainage and irrigation. The level of farmland inside the dikes was lower than the surrounding floodwater or river water, enabling farmers to have ample irrigation water while preventing floods. However, building polder fields exceeded the capacity of individual households and was often completed by wealthy landlords. Tang farmers also popularized the method of raising fish in rice paddies, allowing fish to eat weeds and mosquito larvae while fish manure increased field fertility. During the Tang (and subsequent Song, Yuan, Ming, and Qing), people practiced slash-and-burn cultivation on mountainous land, called "she tian." Before sowing, trees had to be felled, along with shrubs and tall grass. She tian did not use plows or turn the soil and was an extensive cultivation method. After felling trees, people waited for rain before burning the grass and wood on the ground. After the rain, while the ashes were still warm, they sowed seeds without irrigation. The crops planted were dryland ones such as millet or glutinous millet. This extensive cultivation method could not maintain soil fertility and required shifting fallow. Some moved annually, others after two or three years of planting. After leaving, the original land needed seven or eight years to regrow trees and wild grass before slash-and-burn could be repeated. In mountainous areas where she tian prevailed, there was a special group called "she tian fu" who owned no land themselves but specialized in traveling to perform slash-and-burn work for others. They would agree in advance on work for a certain family's she tian. Although she tian fu might travel hundreds of li to arrive on schedule, they brought their own tools. Lingnan and southeastern coast Both the Sui and Tang dynasties sent armies south to Lingnan and colonized the area, clashing with the indigenous peoples. In the waterlogged swamps, the air was very humid, and parasites and mosquitoes proliferated in large numbers. Standing water on the ground and swamps left after river floods allowed Anopheles mosquitoes and malaria to thrive in Lingnan. To northern Han people, the entire Lingnan region was plagued by epidemics, with miasma (malaria) prevalent. Tropical forests were breeding grounds for various parasites. Lingnan's miasma kept the Han out of the low river valleys. At that time, most Han settled in northern Guangdong and Guangxi, where there was no miasma threat, while the Dai indigenous people living in the lower river regions had some degree of immunity to malaria. In multiple Han military campaigns against indigenous peoples, one-quarter of the troops were lost to malaria. Huang Chao's forces also suffered 30–40% mortality from malaria before withdrawing from Lingnan and moving north. The Han were helpless against miasma, and western Lingnan and further west in Yunnan remained under indigenous control. More thorough environmental change in southern China would have to wait until the Han population became larger and denser. During the Tang, most of Lingnan was still covered by forest, but the original deciduous broadleaf forests on the highlands had been burned and replaced by secondary coniferous and fir forests. At that time, the lower reaches of the West, North, and East Rivers were all densely marshy and difficult to cultivate. Indigenous Tai-speaking groups cultivated rice in the lowlands, farming the same land year after year, while the Li, Miao, and Yao in higher mountainous areas practiced shifting slash-and-burn cultivation. They used slash-and-burn methods, constantly migrating, combining agriculture with hunting and gathering. The Moyao people hunted in highland forests after the autumn harvest, burning wild grass to promote new growth and attract deer herds for hunting. The Han did the same with slash-and-burn. In the dry winter months, they burned forests on mountain slopes, then many families together sowed seeds in the ashes, harvesting for a few years before moving to another plot and establishing a new settlement, allowing the original exhausted plot to regrow vegetation. In higher mountainous areas, especially along the watershed between the Yangtze and West Rivers, forests were often cleared to plant tea. Unlike annual crops, tea bushes provided a certain degree of soil protection. Highland residents also used girdling, topping, and felling to clear mountain forests, opening clearings in dense tree canopies to allow sunlight to reach the ground for planting tuber crops such as taro. Slash-and-burn cultivation in the upper reaches of rivers caused erosion in mountainous areas, sending more sediment into the lower reaches of the Xi, Bei, and Dong Rivers, depositing it in the floodplains of the Xi, Bei, and Dong Rivers and becoming fertile soil, while also bringing problems of flooding and malaria. In the Fujian region, the indigenous Yue people spoke Austronesian languages and primarily lived by fishing and hunting, possibly also practicing slash-and-burn rice cultivation. Many places in southern Fujian were saltwater marshes and habitats for saltwater crocodiles. Inland mountains blocked Han entry into the region, so Han arrival on the southeastern coast came much later than in Lingnan. By the 8th century, Han immigration to Fujian began to increase. Locals built river dams and developed rice paddies. The Han not only battled the environment and saltwater crocodiles but also used military force to drive the Yue from the valleys. The Tang established tuntian to control the area. Many indigenous people fled to the mountains, while the remainder accepted Han assimilation. Both the Yue and saltwater crocodiles disappeared, replaced by the Han and their farmland. == Song dynasty ==

North From the Song onward, ecological conditions in the south and north changed relatively. The northern ecosystem gradually deteriorated, with massive forest reduction. The ground lost its temperature-regulating function, average annual temperatures dropped, and the shortened, reducing the growing season for crops. At the same time, rainfall also decreased, turning the north into a semi-arid region. After severe destruction of natural vegetation, soil erosion intensified. Combined with the loose soil of the Loess Plateau, which was easily eroded, most rivers in the north had increased sediment loads, causing siltation and flooding, especially the Yellow River, which gradually became an "elevated river." Its lower reaches frequently changed course. Lakes on the northern plains were successively filled in, eliminating their natural flood storage and detention functions and causing frequent floods. During the same period, the south was still able to maintain ecological balance. Due to higher temperatures and rainfall, the self-regenerating capacity of natural vegetation was stronger. The entire ecosystem was not as fragile as in the north, and the deterioration process was relatively slow. Many small rivers on the North China Plain were blocked by sediment deposition and collectively changed course or dried up. To repair river dikes, local residents felled all trees and shrubs in nearby hills for dike support. Because the North China Plain was very flat, floodwater could not drain, causing waterlogging and salinization of the land. Large areas lost their original vegetation. Wind carried sand and dust across the plain, forming dunes. Lakes and ponds silted up, and the silt quickly became very infertile. Much originally fertile land turned into sandy ground. Jiangnan During the Tang and Song dynasties, people expanded the vast low-lying and marshy plains of the Yangtze Delta through drainage methods, with the Song dynasty being particularly enthusiastic about the effort.. In the low-lying areas of the Yangtze Delta, the government organized substantial human and material resources to construct many large polders (fields created by building dikes to enclose lakes for cultivation), thereby increasing the area of farmland and raising tax revenue. From the late 11th century to the early 12th century, more than of land in the Yangtze Delta region were opened through polder development.. In the Northern Song period, most polders around Tai Lake were organized by stationed troops with strict management; ordinary residents were prohibited from imitating the practice, and the prohibitions were quite rigorous. Around 1112, these restrictions began to be relaxed, and privately managed polders started to appear along the shores of Tai Lake.. A dense network of waterways connected the individual rice paddies, providing both sources of irrigation water and a transportation network. The establishment of polders, together with the introduction of early-ripening, drought-resistant rice varieties, greatly increased total grain output. Farmers discovered that draining the rice paddies once a year improved the soil's performance, fertility, and productivity. In low-lying farmland areas, people divided the polders into smaller plots that were easier to manage, while establishing cross-village cooperative irrigation management mechanisms. This allowed even low-lying or swamp-like fields to be drained once a year. The area under double-cropping expanded continuously, and more and more forests and marshes were converted into farmland.. During the Northern Song, the Tai Lake region in the lower reaches of the Yangtze had fertile land, rare floods, and ecological balance. During the Southern Song, the local population increased significantly, and people enclosed lakes to create fields, causing floods to become more frequent. The Southern Song government initially encouraged the people to widely open polders in the Tai Lake area, which affected the lake's water storage capacity. During flood periods, the water had nowhere to drain, resulting in disasters. The Southern Song government then changed its policy, restored the ban on "stealing" lakes (encroaching on lakes), and even forcibly abolished fields to restore lakes.. in the area of Guilin. Early-ripening rice revolutionized Song dynasty agriculture. By the 13th century, many hilly areas in the lower Yangtze region and Fujian—where water supply or soil conditions had previously been unsuitable for rice cultivation—were transformed into terraced fields. The landscape of the eastern half of China's rice-growing regions underwent a thorough transformation.. Terraced fields became widespread in the Southern Song. On relatively low mountain ridges, terraces were built layer upon layer, extending all the way to the mountain tops. Although the terraces replaced forests on the mountains, they did not cause soil erosion on the slopes. Instead, they retained runoff from the slopes layer by layer, preventing the soil from being washed away and preserving the ecosystem. In contrast, slash-and-burn fields (she tian) in mountainous areas had the opposite effect. These fields did not alter the slope of the mountain land, so the erosive force of rainwater remained strong. After the natural vegetation was burned away, the ground was either left bare or sparsely planted with dryland crops, making it impossible to conserve soil and water and causing severe ecological damage.. Many forests in the Yangtze River basin no longer existed, surviving only in some hilly and mountainous areas south of the Yangtze. Tigers could still find habitat there, but elephants, which preferred to live in low-lying places, had disappeared from the Yangtze basin.. From the Southern Song onward, fish ponds were commonly dug in southern mountain valleys, alluvial plains, or delta plains. Fish fry were raised using residues, garbage, and silkworm feces, producing more food per unit area.. In the mountains south of the Yangtze, the Miao people and Yao people planted Chinese fir trees for trade and profit.. On the other hand, ocean currents carried large amounts of sediment from the new mouth of the Yellow River to the Hangzhou Bay, approximately away, where it was deposited. This increased the land area along the coast of Jiangsu and boosted rice production there.. Central China and Sichuan Before the Northern Song, Dongting Lake in the Jianghan Plain was still expanding, with abundant water volume. During the Northern Song, Dongting Lake reached its maximum width and depth. From the Southern Song onward, as northerners migrated south and grain needs increased, people began enclosing fields for farmland, competing for fertile lake fields. From then on, the lake surface gradually shrank, water capacity declined, and floods caused disasters when they arrived, breaching dikes and inundating fields and houses. At the same time, population growth in the lower Xiang River led many farmers to practice slash-and-burn in mountainous areas, destroying forests and turning local mountains into bare hills. Fortunately, the Xiang River region's forests had strong regenerative capacity. In many areas, after forests were destroyed, secondary forests could grow after several years. Moreover, due to inconvenient transportation in some areas and excessively high mountains that reclamation teams could not reach, some original forests were still preserved. The Song emphasized colonization of Sichuan. After indigenous peoples were assimilated or driven into the forests, Han farmers settled in the river valleys and cleared land. By the 11th century, forests in many areas had been largely felled. Many areas in the region were transformed. Farmers dug hillsides into terraces, stored rainwater, and then planted early-maturing rice varieties. Large areas of forest in Sichuan were felled. The "forbidden mountains" that had once separated Han and indigenous territories were almost completely deforested. South China During the Song, the population of Lingnan continued to increase, but due to fear of malaria, they remained in northern Lingnan and dared not move to other parts of Lingnan. At that time, malaria was mostly found in the alluvial plains of southern rivers rather than upstream areas. From the 11th century, the growth of the Pearl River Delta accelerated. Flood control projects on the Pearl River carried more sediment from upstream to the Pearl River estuary, blocking the view of the sea looking south from Guangzhou. Slash-and-burn agriculture in the upper reaches of the Pearl River system caused soil erosion, sending more sediment down the Dong, Xi, and Bei Rivers. The floodplains in the lower reaches of these rivers, especially where the Dong and Bei Rivers converged, had very fertile soil. These lower river reaches generally flooded every year. As early as 809, the Tang built embankments to prevent the southward-flowing Xi River from joining the northward-flowing Bei River, allowing floodwater to continue flowing downstream. Around 1100, construction began on the Sangyuanwei project, eventually building a dike about long that protected about of land from flooding. This created a new era of agricultural development in the Lingnan region. At the same time, seawalls were built in Leizhou Prefecture and western Dongguan, creating nearly of coastal defense dikes that blocked periodic tides and typhoons, adding of arable land. However, coastal mangrove forests also disappeared as a result. In the Song dynasty, a total of 28 dike enclosures were constructed along the upper reaches of the Pearl River, with a combined length of 66,024 zhang, protecting 24,322 qing of farmland. The flood-control dikes confined the rivers to fixed channels so that, during the rainy season, the water would not overflow or burst into multiple channels. Instead, the river water flowed directly into the bay area, turning the former floodplains into land suitable for agriculture. By draining the swamps and waterlogged areas created by flooding, the ecological environment of the malaria vector Anopheles mosquito was altered, making these regions less dangerous to Han Chinese settlers.: 75–76 In the mountainous areas north of Guilin, densely growing cinnamon trees produced cassia bark (cinnamon spice). By around the year 1000, most of the original forests around Guilin had been felled.: 160 Land ownership During the Song, mountain and forest property rights underwent nationwide changes, with private ownership of mountains and forests fully recognized. Previously, mountains and forests belonged to the state. People could use mountain and forest resources but could not occupy or reclaim them. During the Song, almost all plain land had already been reclaimed. The government allowed people to legally occupy mountains and marshes, so people began large-scale competition with mountains for land and with water for land. Many mountainous slopes were transformed into terraces, while others became she tian with slash-and-burn cultivation. In some mountainous areas limited by conditions and unable to be reclaimed as fields, they were turned into private forest farms for growing trees. In other mountainous areas that were too steep and inaccessible, mountain owners simply left them idle, retaining only ownership rights but finding it difficult to utilize them. Some mountainous areas remained state-owned forests, but the scope of such forest areas gradually shrank. The government's basic attitude was to open mountains and forests as much as possible, only choosing to close certain forest areas. There was essentially no management of state-owned forests, which were open to anyone for felling, with only slight tax collection called "choufen." During the Northern Song, enclosing lakes for farmland around Tai Lake in the Jiangnan region was prohibited and called "stealing lakes." By the early Southern Song, as large numbers of northern residents migrated south, to supply food, the government officially recognized enclosing lakes for farmland as legal and even used government power to promote it. As a result, lake enclosure for farmland quickly spread throughout Jiangnan. Countless small lakes were soon enclosed and filled, while larger lakes also rapidly shrank. == Yuan dynasty ==

North The Mongols massacred people and attempted to turn all of northern China into their pastureland. Wherever Mongol armies went, city walls and agricultural facilities were razed to the ground. Dams no longer existed, irrigation canals were cut, leaving behind swamps. Grain seeds were burned, fruit trees were sawed down, shelterbelts were felled to the ground, and farmland became desolate, dry grassland exposed to wind and sand. It was not until the reign of Kublai Khan that the practice of turning northern land into pasture was prohibited. The Yuan construction and maintenance of the Grand Canal greatly altered the environment of the North China Plain. To maintain canal water levels and prevent water from draining into the Yellow River, Huai River, or Yangtze River, in addition to using sluice gates and weirs as barriers, people also had to redirect and block small streams and rivers flowing westward into the Shandong Peninsula to ensure all river water entered the Grand Canal. Sediment brought by the Yellow River and its tributaries would deposit in the canal, requiring regular dredging. Dense maintenance was needed at the intersections of the canal with several major rivers. The government had to invest large resources to maintain canal operations; otherwise, its water system could collapse, bringing flood disasters to the North China Plain. After the Yuan changed the Yellow River's course, the abandoned northern channel became a source of sediment. When winds rose, sandstorms ravaged the entire North China region. During the Jin, when the Yellow River changed course southward, Juyeze lost its water source. Water receded and sand remained, creating large areas of shoals that were reclaimed by nearby residents. In 1180, the Jin government even sent envoys to recruit refugees for tuntian in Liangshan Marsh. Smaller lakes silted up into flatland even earlier. During the Southern Song, officials responsible for irrigation and canal systems began worrying about upstream deforestation and noted the impact of salinization and flooding on downstream areas. By the 14th century, the construction of the Grand Canal had changed the drainage network of the North China Plain. Newly built dikes in the Yellow River basin diverted all of the river's flow into the lower-lying Huai River.. The Yuan dynasty paid relatively greater attention to flood control in the Jianghan Plain. It prohibited polder construction around Dongting Lake, converting fields back into lakes, and reopened blocked outlets along the Yangtze that had been sealed during the Southern Song, allowing water to disperse. By the Dade era (1297–1307), a total of six outlets had been reopened.. South China Along the Pearl River, the Yuan dynasty not only repaired the old dike enclosures built in the Song but also constructed 34 new ones. The total length of the dikes reached , protecting about 20% of the cultivated land in Guangdong.. Out of fear of the Mongol invaders, between 1273 and 1274 many residents and clans from in northern Guangdong fled south and settled on small islands at the mouth of the Pearl River. They "intercepted" sediment and reclaimed new farmland on sandbars. These newly reclaimed areas were called "sand flats" (沙坦) or "sand fields," (沙田) new land parcels formed by silt deposition.. When the sandbars gradually rose close to the water surface, people placed rocks around them to stabilize the existing sediment and trap more deposits. After building stronger enclosures, beans could first be planted on the sand flats, followed by rice. Chains of sand flats formed tens of thousands of mu of farmland, creating the Pearl River Delta. At the same time, accelerated erosion of abandoned mountainous land in northern Guangdong due to the Mongol invasion sent more sediment from the Dong River to the Pearl River mouth, speeding up sand flat formation.. In the 14th century, formation of the Pearl River Delta accelerated further. Alluvial sandbars appeared along the coast at the mouth of the Dong River, and Xiangshan Island gradually connected to the mainland.. The Mongol invasion also caused population growth in the southwestern coastal areas of Guangdong. On the Leizhou Peninsula, people cleared large areas of tropical rainforest and mangrove for reclamation, followed by slash-and-burn practices, causing permanent damage to the local environment. Many areas turned into wasteland.. ==Ming dynasty==

North China Before the Ming dynasty, dense forests still existed in the Great Wall region. By the Ming, forests on the Loess Plateau were heavily damaged. In the early Ming, forests in Luya Mountain and Yunzhong Mountain in northwestern Shanxi, and Heng Mountain in northern Shaanxi, remained intact. Some damaged forest areas in the Guanzhong Qinling and Xiao Mountains also partially recovered. After Yongle established the capital in Beijing, the Taihang Mountains became a major source of timber for the city, greatly accelerating deforestation. As the imperial palace and urban development required wood, the government conducted large-scale logging and charcoal production. After prolonged uncontrolled official and private exploitation, the forests in the Great Wall region suffered devastating destruction. After the mid-Ming, large areas of forest disappeared. By around the 17th century, fuel and construction timber were generally in short supply. Rapid population growth led to continuous reclamation of new farmland and increased demand for daily timber, causing a sudden change. Forest areas shrank quickly. Forests in the Heng Mountains and Lüliang Mountains were successively exhausted. At this point, the massive building materials needed for the capital could no longer be obtained from the middle reaches of the Yellow River and had to be sourced from Sichuan and the Two Lakes region. Due to thorough destruction, the forests' self-renewal capacity was almost lost. The middle reaches of the Yellow River presented a continuous sight of bare mountains. Although the Ming had policies prohibiting logging, their main purpose was to protect the feng shui of imperial tombs or to meet military and political needs. The scope was very limited and showed no genuine ecological awareness. In North China, the opening of the Grand Canal slowed the discharge of all rivers, large and small. Sediment continued to accumulate, causing periodic flooding and waterlogging. Because the river water contained salt, waterlogged land easily underwent soil salinization, becoming uncultivable. The worst areas turned into swamps, which then bred locusts. The Beijing-Hangzhou Grand Canal further impeded the already slow-flowing Yellow River and forced the Huai River to backflow into its upper reaches. Sediment from the Grand Canal and Yellow River frequently blocked the mouth of the Huai River, causing floods to spread into the plain. Frequent flooding covered farmland with sand and gravel, sometimes up to 7–8 meters thick. Some formerly prosperous counties with fragrant rice and abundant fish saw large areas of land salinized, turning into barren red earth where even weeds would not grow. Weeds that grew after floods became breeding grounds for locusts. Due to insufficient irrigation, agriculture was limited to drought-resistant crops such as winter wheat, sorghum, and soybeans.. In 1578–1579, Ming official Pan Jixun managed the lower Yellow River by building earthen and stone dikes, dredging the riverbed, and unifying the Yellow River's course. He proposed the method of "constricting the water to attack the sand," using higher and narrower dikes to accelerate flow. Water was constricted within "lǚ dī" near the banks. His river management increased sediment at the sea mouth, lowered the downstream gradient, and diverted clear water into the Yellow River to scour silt from the riverbed. In 1579, Pan Jixun built the across the Huai River, storing clear water from the Huai and two other rivers in Hongze Lake. Continuously raising the Gaojia Weir on the eastern shore of Hongze Lake ensured the lake's water level remained higher than the Yellow River, allowing grain-transport boats to pass. Southwest Urban residents' demand for timber prompted mountain residents to specialize in logging and timber transport. The Yunnan-Guizhou region, previously economically undeveloped with sparse settled agricultural population and inhabited mainly by non-Han indigenous peoples, developed under Ming rule into a region increasingly dominated by Han migrants and commercialized. The southwest had rich and diverse ecosystems. In southernmost Yunnan's Xishuangbanna, rolling mountains and dense rivers existed. The Khmu people lived deep in jungles and bamboo forests, practicing slash-and-burn agriculture (continuing into the 20th century) and domesticating elephants. The southwest originally had a healthy ecosystem with tigers and elephants frequently appearing and vast forests. Thai-speaking peoples cleared some river valleys into farmland, while other ethnic groups practiced slash-and-burn. Due to high mountains and deep valleys that were difficult for humans to access, human impact was minimal. From around 1400, large numbers of Han people arrived in Yunnan and Guizhou. The Ming-established weisuo and military farms spread across the southwest, with 250,000 Han soldiers beginning to farm in river valleys. Indigenous groups' wooden tools could only reclaim lighter alluvial soils in valleys and were unsuitable for the heavy soils of forested areas; they also lacked oxen for plowing. The Ming equipped Han migrants with iron plows and tens of thousands of oxen, enabling them to reclaim forest soils. In the 15th and 16th centuries, millions of *mu* of farmland were opened in Yunnan and Guizhou. During court wars against indigenous peoples, Han armies set fire to mountains, destroying animal habitats. The ultimate solution to rebellions was to transform different ecological environments into farmland. In Guizhou, some local tusi also led people to shift from slash-and-burn to plow-based production.. Northwest The Ordos Desert in the Yellow River Hetao region had varied ecosystems—some purely desert, others grasslands suitable for nomadic life. Here, water from the Yellow River could be diverted for irrigation, allowing Han people to settle and farm. In the late Ming, a total of of canals had been dug in the Hetao region, irrigating thousands of *mu* of land. The Ming built the Great Wall in the Ordos to separate the grassland from agrarian society. It ordered stationed troops to burn 50–100 *li*-wide strips of wasteland north of the Great Wall (at least in strategic locations) each year, depriving Mongol cavalry horses of fodder, destroying pastures so Mongol herders could not enter, but sowing the seeds of desertification. Converting forest and grass vegetation to farmland also tended toward desertification as soil organic matter decreased. Jiangnan and Central China During the Wanli era (1573–1620), several reclamation fields of over one thousand hectares each had been opened along the Yangtze and its tributaries in Anhui. In central China, Hongwu Emperor established military farm weisuo in Hubei, repaired old dikes, and built new water conservancy facilities, recruiting migrants to reclaim land. These policies continued into the 16th century. People built dikes on the southern bank of the Han River, preventing water from overflowing. The riverbed rose higher and the current became faster, greatly increasing flood risk downstream. As a result, downstream residents began building dikes to protect their homes and then reclaimed more swamps and lakes. By the late Ming, the hydrological conditions of the entire Han River basin had been thoroughly transformed by humans. In the 15th and 16th centuries, large numbers of people migrated to Hunan, introducing advanced rice cultivation techniques from the lower Yangtze. They built dikes around swamps and tidal flats to form polders for flood control and irrigation, transforming the area into rice fields. Some early polders were very large, reaching thousands or tens of thousands of *mu*. Xu Guangqi already recognized human causes of flooding. He criticized powerful local families for encroaching on swamps, lakes, and riverbank alluvial plains, filling water bodies to create fields, which increased flood risk and harmed entire settlements. Southern mountainous areas Before the Ming, there were only a few settlements in hilly and mountainous areas. Most terraced fields followed riverbanks near cities. In most regions, reclamation of hills and mountains began in the late Ming. After mountain forests were privatized, some private forests in the south survived. After timber was cut and sold, mountain owners would replant to regenerate them. During the Ming and Qing, private forestry was common, especially in southern Anhui and Fujian. Mountain tribes south of the Yangtze specialized in cultivating Chinese fir and producing timber. At this time, public forest resources were becoming exhausted, while private plantations grew trees for sale, yielding good profits. Mountain owners did not necessarily manage the forests themselves but could lease them to others. In general, private plantations were well protected with high survival rates for replanting, in stark contrast to the destruction of public forests.. After the mid-16th century, planting Chinese fir became prevalent in southeastern mountainous areas. Broadleaf forests turned into coniferous forests such as fir. Small animal populations in the mountain forests decreased, tigers faced food shortages and increasingly attacked livestock in the plains, while Asian black bears and wolves that once lived in broadleaf forests gradually became extinct.. On the other hand, the Ming issued orders to protect monastery forests to maintain the natural environment around temples. from the Americas In the Yangtze basin and Lingnan, lowland farmland became increasingly insufficient. New migrants, seeking arable land, had to penetrate deep into the mountains and learn various skills from locals. In the first half of the 16th century, New World crops from the Americas—maize, potato, sweet potato, peanut, and tobacco—spread to China, exerting a huge ecological impact. Han people migrating into the mountainous border regions of Jiangxi, Fujian, and Guangdong formed the origin of the Hakka people. The Hakkas merged and assimilated with the local indigenous She people. Around 1500, the mountainous border of the three provinces became Hakka territory. Their dialects and customs differed markedly from those of lowland Han. The Hakkas cleared mountain forests and widely planted maize and sweet potatoes, selling mountain products outward. Hemp, ramie, indigo, tea, sugarcane, and tobacco were the most common cash crops planted by Hakkas. From the mid-16th century onward, Hakkas began migrating to mountainous areas across southern and southeastern China, selling products to riverside towns. They also rented large mountainous lands from Han landlords and recruited poor She people to clear forests using slash-and-burn methods. In the 16th and 17th centuries, large numbers of Hakka and She men migrated northward into the mountains of Jiangxi, Anhui, and Zhejiang, becoming mobile populations known to the government as "shed people" (*pengmin, 棚民). They built temporary sheds, developed mountain land, and moved on after exhausting the soil. In the mountainous areas of the Gan River basin in Jiangxi, most land had previously been densely forested and untouched by Han logging until the arrival of the shed people. Many shed people in Jiangxi mountains were miners, loggers, and papermakers. Their food mainly came from slash-and-burn on forest edges, gradually damaging the Jiangxi mountain environment. Hainan Island Hainan Island had numerous coral reefs and oyster breeding areas in the north. The island was covered with various tropical forests containing over 3,500 plant species. Indigenous Li people practiced slash-and-burn to grow mountain yams and upland rice, supplemented by forest hunting and gathering. Due to their small population, their impact on the ecosystem was limited. During the Ming, the amount of cultivated land on Hainan doubled, from about 2 million *mu* around 1400 to 3.8 million *mu* in 1615, most of it farmed by Han people. Hainan had been transformed to become suitable for Han habitation. The government encouraged Han people to burn forests in river valleys and mountains. Continuous burning created opportunities for tropical cogongrass to grow. ==Qing dynasty==

In the mid-Qing, China's forests and vegetation suffered the most severe destruction. The Qing population expanded rapidly—from only 80–90 million in the early Qing to about 268 million by 1776, marking China's first population explosion. Over the hundred-odd years of the mid-Qing, China's ecological environment suffered unprecedented fatal destruction. First, most of the forests remaining from the early Qing disappeared entirely. Second, bare mountains and ridges without vegetation protection suffered erosion by rain, carrying away mud and sand. Third, downstream rivers became silted and obstructed, leading to frequent floods. Fourth, large amounts of sediment washed onto plain farmland, causing slow desertification of cultivated land and declining productivity. By 1800, South China tigers could barely survive only in a few mountainous areas on the borders of Guangdong and Jiangxi and in Fujian. Asian elephants were pushed to remote areas on the border of Yunnan and Burma. By the early 19th century, almost no part of China remained undeveloped by humans. Completely "natural" areas untouched by humans were extremely rare. Most land had been farmed. The scope of primitive natural areas continued to shrink, with the remainder mainly the most remote and inaccessible high mountains, deep valleys, and underground rivers. Forests Deforestation During the mid-Qing Qianlong (1736–1796) and Jiaqing (1796–1820) reigns, the nation's forests suffered unprecedented severe destruction. After each flood breach, areas reached by river water turned into swamps. When they dried, the plain sometimes became a saline-alkali desert difficult to cultivate. Siltation of the water transport system made the entire region even more vulnerable during floods. Major drainage areas and shallow lake zones that had once served as floodplains gradually disappeared, so that even slightly excessive rainfall endangered local crops. Between 1645 and 1855, the southern course of the Yellow River experienced a flood once every 1.89 years on average. As the court withdrew from Yellow River management, the water conservancy management system on the North China Plain severely shrank and ecological balance collapsed. Migrant mining and farming activities rapidly changed Rehe's forest environment. The Mulan Enclosure was also opened to land buyers. By the late 19th century, the Qing finally decided to open the hunting ground to agriculture. Some basins and river valleys remained undeveloped. Although shed people had already migrated there in the Ming, their numbers were still small. In late 17th-century Taiwan, travelers in the countryside were completely submerged by wild plants. As the number of Han guest migrants increased, reclamation of arable land gradually expanded into mountainous areas. The Qing government attempted to separate Han and indigenous peoples. In 1722 it erected stone markers as boundaries, prohibiting Han from further migrating into the territory of Gaoshan indigenous peoples. It established a "fan boundary" separating Han and indigenous peoples. These boundaries were usually located at the junction of plains and mountains and were quite effective in blocking Han entry into mountains for logging.. Due to population pressure, the Qing government eventually conceded and no longer prohibited Han reclamation of indigenous land. At the time, the Qing court's logging targets were limited to camphor wood. There was no need to climb into high mountains, so Taiwan's forests were not heavily depleted. By the 19th century, the western plains of Taiwan had become very similar to those in Fujian and Guangdong. Large deer herds had disappeared, forests had been cleared, and Han settled agriculture had triumphed. In 1875, Shen Baozhen abolished the prohibition on crossing the fan boundary. In the following 20 years, ordinary Han people could, after paying a fee, freely use mountain forest resources. From the late 1880s, the Qing government implemented various "" measures, breaking the previous separation between Han and indigenous peoples and allowing farmers to develop tea and camphor plantations. To produce camphor, Han people cut camphor trees in the mountains. Areas where camphor had been cut were usually converted to farmland, making forest loss irreversible. However, before the ceding of Taiwan in 1895, camphor production was not yet very large. Southwest Before and after the Qing occupied the southwest, merchants and the government caused great environmental damage through logging and mining (iron, copper, silver, tin, etc.). In the early 18th century, the Qing government adopted more active colonization policies and more Han people migrated into Yunnan. The Yongzheng Emperor sought to obtain mineral and timber resources in the southwest and implemented the policy. Han soldiers continued to acquire land from indigenous peoples. The introduction of American crops and reclamation techniques learned from Hakkas and shed people meant Han activities were no longer limited to river valleys but could penetrate the vast forests covering the mountains of the southwest. They rapidly cut trees. By the early 19th century, the deep mountains and dense forests of southern Yunnan had almost disappeared, replaced by dense crops and tea forests on the mountains. However, the short tea bushes were insufficient to block rainwater and protect soil. In the mid-18th century, copper mining in Yunnan reached its peak. Smelting copper required charcoal. At the height of Yunnan copper production, annual output exceeded ten million *jin*, requiring over 100 million *jin* of charcoal. As a result, forests near the mines were completely logged. Fuel exhaustion came faster than the depletion of ore deposits. Once old forests were exhausted, ecological damage further aggravated flooding. Northeast The Qing decided to seal off its ancestral homeland in the northeast to maintain Manchu military strength and ethnic identity. By building and planting the "Willow Palisade", it isolated Han people outside the northeast region. Although Manchus also engaged in some farming in river valleys, most of the northeast was covered with primary pine forests teeming with wild animals, including Siberian tiger, brown bear, mink, sturgeon, and stork, as well as ginseng growing in the forests. The Qing government purchased various foods from the northeast. By the early 18th century, supply shortages began to appear. Pine nuts and pine cones had once been easy to collect. By the late 18th century, the only way to obtain them was to cut down the trees. After 1822, bannermen could no longer catch bears and leopards to send to Beijing. After the Jiaqing era (1796–1820), Han migrant reclamation zones extended upstream along the Songhua River. Large-scale agriculture was already underway in Jilin. After 1860, the Qing changed policy to "migrate to strengthen the borders" in order to increase tax revenue. Large numbers of Han began migrating into the northeast. By the late Qing, the northeast population had surged to 17 million, leading to further development extending to Heilongjiang. Primary forests in the northeast were greatly depleted. When the northeast and Siberia were developed due to railway construction, China signed a treaty to supply railway ties and established two joint forestry companies. This marked the beginning of modern-style development of northeast forest resources, mainly carried out by Russian and Japanese companies. Northwest In the Qing northwest, grasslands shrank and were converted to farmland, with desertification accelerating. After the Kangxi era (1662–1722), reclamation expanded into mountainous areas, causing irreversible destruction of forests in Shaanxi, Gansu, Qinghai, and Ningxia. This led to soil erosion, ecological imbalance, species degradation, and even extinction. One consequence was desertification of grasslands in northern Shaanxi, Gansu, and Ningxia. Combined with warfare and burning, when the Qing used troops in the northwest it ordered the burning of pastures to defeat the enemy, severely damaging the ecological environment and forming the Mu Us Desert spanning Inner Mongolia, Shaanxi, and Ningxia. The and Ordos Plateau in Inner Mongolia were originally covered with grassland and forest. In the mid-Qing, large-scale land reclamation occurred and desertification began. In the mid-18th century, the Qing government introduced policies of "migrate to strengthen the borders" and "borrow land to support the people." Desert gradually formed within 100 *li* south of the Ming Great Wall in northern Shaanxi.In the late 19th and early 20th centuries, the Qing government and Mongol nobles sold natural grasslands originally used for grazing in the Horqin area to Han farmers. After several years of farming, the loose topsoil was blown away. Wind erosion turned farmland into desert and pastures deteriorated. Cattle herds could only be kept in constantly shrinking areas. Around 1900, the Qing court allowed and even encouraged Han colonization of Mongol regions to strengthen national defense and increase revenue. Many Mongols also became farmers. in Xinjiang In the northwest, the Qianlong Emperor defeated the Dzungar Khanate, nearly exterminating the Dzungars and leaving the Dzungar region as empty space to be filled by Han farmers, Manchu bannermen, and Hui people. Through , Chinese armies transformed fertile, water-source grasslands into farmland. Where there were rivers formed by melting snow, desert land around oases in the Tarim Basin was also reclaimed. Between 1760 and 1820, more than one million *mu* of land were opened as fields. After these grasslands were plowed, they likely caused soil erosion and desertification of the grasslands, making recovery to their original state difficult. Natural forests in Xinjiang were distributed in the Altai Mountains and Tian Shan areas. Due to poor management and unrestricted logging, large areas of dense forest disappeared. In arid and semi-arid regions, land reclamation depended entirely on building irrigation channels. Although beneficial to farmland, these harmed neighboring water users. Xinjiang used the karez irrigation method, transporting snowmelt from the mountains to farmland, allowing deserts to prosper. In the early 1840s, Lin Zexu established irrigation channels in Xinjiang, directing water from the Tian Shan range to areas with well-organized irrigation for agricultural use. However, the project also restricted water resource use in the area, harming existing farmland and pastureland. In the Hexi Corridor region, during the mid-Qing many people entered the Qilian Mountains to log. After forests disappeared, mountain snow lost shade and melted immediately when spring warmed. Water had nowhere to be stored, causing floods. In autumn when water was needed, there was none. Thus, since the mid-Qing, the frequency of both floods and droughts in the Hexi region greatly increased. West In the Qing, the only human agricultural ecosystem that did not experience environmental degradation was the Sichuan Basin around Chengdu. Local agriculture was intensive and carefully cultivated trees, including bamboo, tung oil tree, mulberry, Chinese fir, lacquer tree, and various fruit trees. The local climate was humid with lush vegetation. The Chengdu Plain always had a good irrigation system. The Dujiangyan water conservancy project built in the Qin dynasty still operated well. Every farm had its own small patch of bamboo, Chinese fir, palm, tung oil tree, lacquer tree, or fruit tree forest. Many trees also grew along the Min River, creating lush greenery. Many places on the Tibetan Plateau originally had forests. Over thousands of years, these primary forests were cleared by Tibetans and replaced with low-growing plants with high regenerative capacity that could feed cattle and sheep, such as grasses, clump plants, and creeping plants. Under moderate grazing, they formed rich, knee-high low-grass vegetation. This vegetation could conserve soil and water. Although forests were cleared, mountain slopes did not become barren but became pastures for Tibetan herds, also avoiding soil erosion and ecological problems for the downstream Sichuan Basin. ==Republic of China==

Mainland period Resource problems In the early 20th century, deforestation and the resulting severe soil erosion and land salinization became one of the main factors in China's underdeveloped agriculture. Fishermen used very fine-mesh nets, catching large numbers of juvenile fish and fish eggs, leading to the collapse of nearshore fish stocks. After the flood receded, silt buried large areas of farmland, making them uncultivable. In some flooded areas, Yellow River flooding raised the groundwater table, causing the covered land to undergo salinization. As the economy began to industrialize and no longer relied on the agricultural and forestry sectors to earn foreign exchange, logging speed slowed from 1972 onward. By the 1990s, logging had in principle stopped, and old forest farms were converted into forest recreation areas. Civil conservation groups designated 1999 as the Year of Forest Culture and launched a forest protection movement. After 2000, illegal logging and reclamation still occurred, but the proportion of area affected was not high. Water pollution Taiwan's water pollution sources are mainly divided into three categories: municipal wastewater, industrial wastewater, and livestock wastewater. In the 1970s, industrial wastewater was the main source of water pollution. In early 1986, continuous mass die-offs of farmed oysters and tiger shripms fry occurred along Taiwan's southwestern coast. The root cause was water quality pollution. The government immediately legislated continuous daily fines for major polluting industries or factories in severely polluted river basins that frequently discharged sewage without improvement, to prompt polluters to improve anti-pollution equipment as soon as possible. Since 1993, total wastewater volume has gradually decreased. The proportions of industrial wastewater and livestock wastewater have relatively declined, while the proportion of municipal wastewater has relatively increased. Taking 2017 as an example, total sewage discharge was 657.47 million tons per day, of which municipal sewage reached 531.58 million tons per day (80.85%), industrial wastewater only 55.25 million tons per day (8.4%), and agricultural wastewater 70.65 million tons per day (10.75%). At present, industrial wastewater in Taiwan has been brought under considerable control. As for municipal wastewater treatment rates, the whole of Taiwan had only 33.7% at the end of 2006, showing that construction of sewage sewers urgently needs strengthening to reduce municipal wastewater. Various wastewaters are discharged or seep from pollution sources, polluting rivers, reservoirs, groundwater, and marine water bodies. In 1987, the length of severely polluted rivers accounted for 11.4%. In 2003, river pollution reached its peak, with severely polluted sections accounting for 15.8%. Thereafter, over the more than ten years from 2004 to 2017, river pollution levels improved, accounting for only 7.6–3.5%. However, improvements in river water quality, apart from pH value, are still far from ideal. Environmental protection From the 1970s, Taiwan began to pay attention to environmental pollution and ecological conservation issues, and from the 1990s onward placed greater emphasis on environmental protection and sustainable development. From the 1970s, environmental issues became openly discussed social problems. People began to believe that public hazards and pollution were important problems in Taiwan and that weak public authority was the main cause of environmental deterioration. In the 1980s, the environmental movement arose. Civil movements opposing government environmental policies continued to appear, repeatedly changing government development policies. From 1971 onward, the government successively formulated new environmental laws and regulations, including the *National Park Law*, *Air Pollution Control Act*, *Slopeland Conservation and Utilization Regulations*, etc. For coastal environmental protection, in the 1980s the government announced and implemented the "Taiwan Coastal Natural Environment Protection Plan" as the management basis for 12 protected areas including the Tamsui River mouth. After the establishment of the Environmental Protection Administration, Executive Yuan in 1987, the government made greater efforts in environmental protection. In the same year, the Executive Yuan issued the *Current Stage Environmental Protection Policy Guidelines*, setting the goal of "protecting the natural environment, maintaining ecological balance, and seeking sustainable use across generations" and stating that citizens and industries have the responsibility to work with the government on environmental protection. Environmental protection and economic development should be considered together.. Before 1990, government enforcement of environmental regulations was low. Long-term low-level control meant businesses had no incentive to complete required matters according to law, leading to serious heavy pollution. Only after 1990 did enforcement improve. To prevent air pollution, Taiwan established 85 air quality monitoring stations and set indicators. In the 2000s, increases in the number of days with air quality monitoring and good ratios showed that air quality had improved. In wildlife protection, by 2009 Taiwan had established 85 nature reserves with a total area exceeding one million hectares, including 17 wildlife protection areas. ==People's Republic of China==

Logging In 1950, forest cover on the Chinese mainland had shrunk to 5%–10% During the Cultural Revolution, the government openly viewed forests as an inefficient use of land that should give way to grain or fruit trees. It also proposed "take grain as the key link" and "ask grain from barren mountains," resulting in large areas of forest being destroyed, especially in southwestern provinces such as Yunnan and Sichuan. In the 1960s, most tree-planting plans were unsuccessful. More than half of the trees died due to lack of water. The trees that survived were often plundered by local farmers for fuel and building materials. Desertification continued in the Three-North Shelter Forest region, raising doubts about whether the project could ultimately succeed. Forests under People's Republic of China government statistics are often composed of single tree species rather than the multi-species mixtures of natural forests. Single-species forests, whether pine, poplar, eucalyptus, or rubber tree, are more like plantations and cannot support wild species survival. For example, in Yunnan, rubber plantations replaced tropical rainforest. Although they could supply valuable rubber, they destroyed the habitat of gibbons. Such vegetation can conserve soil and water and achieve carbon capture and storage, but few animals can grow healthily in it. In early 2024, monitoring detected 193 fish species, an increase of 25 species from 2020. Environmental protection policy In 1979, the central government formulated the *Environmental Protection Law (Trial)*. In 1989 it formulated the *Environmental Protection Law*, establishing systems for environmental impact assessment, , and time-limited improvement. In 1989 the central government also established the National Environmental Protection Agency (later upgraded to the State Environmental Protection Administration and the Ministry of Environmental Protection), mainly responsible for implementing environmental laws and regulations. The National People's Congress passed many environmental protection laws, but local governments often failed to implement these orders. Local governments placed more emphasis on creating revenue to increase taxes and thereby obtain rewards or promotions than on environmental protection. By the 1990s, people began to understand sustainable development, the resilience of nature, and the importance of working with natural forces. Environmental protection departments focused on exposing illegal polluting enterprises, but many banned enterprises resumed operations after a period. When polluting enterprises accounted for a large part of government tax revenue, local cadres often did not take strict measures against them. If the environmental protection bureau director took strict measures, his own position might be threatened, leading to incomplete handling of polluting enterprises. ==References==