Urban ecology

's centre during the early 1970s was one of the materializations of Jean-Marie Pelt's works on urban ecology. Historically, ecology has focused on natural environments, but by the 1970s many ecologists began to turn their interest towards ecological interactions taking place in and caused by urban environments. In the nineteenth century, naturalists such as Malthus, De Candolle, Lyell, and Darwin found that competition for resources was crucial in controlling population growth and is a driver of extinction. This concept was the basis of evolutionary ecology. Jean-Marie Pelt's 1977 book The Re-Naturalized Human, Brian Davis' 1978 publication Urbanization and the diversity of insects, and Herbert Sukopp et al.'s 1979 article "The soil, flora and vegetation of Berlin's wastelands" are some of the first publications to recognize the importance of urban ecology as a separate and distinct form of ecology the same way one might see landscape ecology as different from population ecology. Forman and Godron's 1986 book Landscape Ecology first distinguished urban settings and landscapes from other landscapes by dividing all landscapes into five broad types. These types were divided by the intensity of human influence ranging from pristine natural environments to urban centers. Early ecologists defined ecology as the study of organisms and their environment. As time progressed urban ecology was recognized as a diverse and complex concept which differs in application between North America and Europe. The European concept of urban ecology examines the biota of urban areas, the North American concept has traditionally examined the social sciences of the urban landscape, as well as the ecosystem fluxes and processes, and the Latin American concept examines the effect of human activity on the biodiversity and fluxes of urban ecosystems. A renaissance in the development of urban ecology occurred in the 1990s that was initiated by the US National Science in funding two urban long-term ecological research centers and this promoted the study of urban ecology. The field of urban ecology is rapidly expanding, with an increasing number of dedicated research centers emerging. Among the pioneers are the Urban Ecology Research Laboratory (UERL) at the University of Washington, established in 2001, and the Urban Ecology Laboratory (LEU) at the Costa Rican Distance University, founded in 2008. The UERL in Washington specializes in analyzing urban landscape patterns, ecosystem functions, modeling land cover changes, and developing scenarios for urban adaptation within the state. In contrast, Costa Rica's LEU holds distinction as the world's first research center exclusively devoted to studying tropical urban ecosystems. Research conducted there spans various facets of urban ecology, including biodiversity, the impacts of climate change on cities and their surrounding areas (particularly tropical highlands), and the intricate interactions between human activities and urban environments. == Methods ==

Since urban ecology is a subfield of ecology, many of the techniques are similar to that of ecology. Ecological study techniques have been developed over centuries, but many of the techniques use for urban ecology are more recently developed. Methods used for studying urban ecology involve chemical and biochemical techniques, temperature recording, heat mapping remote sensing, and long-term ecological research sites. Chemical and biochemical techniques Chemical techniques may be used to determine pollutant concentrations and their effects. Tests can be as simple as dipping a manufactured test strip, as in the case of pH testing, or be more complex, as in the case of examining the spatial and temporal variation of heavy metal contamination due to industrial runoff. In that particular study, livers of birds from many regions of the North Sea were ground up and mercury was extracted. Additionally, mercury bound in feathers was extracted from both live birds and from museum specimens to test for mercury levels across many decades. Through these two different measurements, researchers were able to make a complex picture of the spread of mercury due to industrial runoff both spatially and temporally. Other chemical techniques include tests for nitrates, phosphates, sulfates, etc. which are commonly associated with urban pollutants such as fertilizer and industrial byproducts. These biochemical fluxes are studied in the atmosphere (e.g. greenhouse gases), aquatic ecosystems and soil nematodes. Broad reaching effects of these biochemical fluxes can be seen in various aspects of both the urban and surrounding rural ecosystems. Temperature data and heat mapping Temperature data can be used for various kinds of studies. An important aspect of temperature data is the ability to correlate temperature with various factors that may be affecting or occurring in the environment. Oftentimes, temperature data is collected long-term by the Office of Oceanic and Atmospheric Research (OAR), and made available to the scientific community through the National Oceanic and Atmospheric Administration (NOAA). Data can be overlaid with maps of terrain, urban features, and other spatial areas to create heat maps. These heat maps can be used to view trends and distribution over time and space. Remote sensing allows collection of data using sources including satellites.|alt=Map of urban tree canopy in Boston. Remote sensing allows collection of data using sources including satellites. Remote sensing is the technique in which data is collected from distant locations through the use of satellite imaging, radar, and aerial photographs. In urban ecology, remote sensing is used to collect data about terrain, weather patterns, light, and vegetation. One application of remote sensing for urban ecology is to detect the productivity of an area by measuring the photosynthetic wavelengths of emitted light. Satellite images can also be used to detect differences in temperature and landscape diversity to detect the effects of urbanization. There are currently two active urban LTERs: Central Arizona-Phoenix (CAP), first launched in 1997 and housed at Arizona State University and Minneapolis-St. Paul Metropolitan Area (MSP). The Baltimore Ecosystem Study (BES) was originally funded in 1998 as an urban LTER but as is no longer funded by the National Science Foundation as of 2021. == Urban effects on the environment ==

Humans are the driving force behind urban ecology and influence the environment in a variety of ways - urbanization being a key example. Urbanization is tied to social, economic and environmental processes. There are six core aspects: air pollution, ecosystems, land use, biogeochemical cycles, water pollution, solid waste management, and the climate. Urbanization was driven by migration into cities and the rapid environmental implications that came with it; increased carbon emissions, energy consumption, impaired ecology; all primarily negative. Despite the impacts, the perception of urbanization at present is shifting from challenges to solutions. Cities are home to an abundant amount of financially well-off, knowledgeable and innovative initiators who are increasing the involvement of science in urban policy processes and concepts. The intersection of the multiple processes/integrated systems approach which can easily emerge within a city, includes five characteristics that can emphasize this fundamental shift at a low cost. These solutions are integrated, comprehensive, multifunctional approaches that speak to the social, economic, and cultural contexts of cities. They take into account the chemical, biophysical, and ecological aspects that define urban systems, including lifestyle choices that are interlinked with the culture of a city. However, despite adapting the opportunities that a city can participate in, the results of the concepts that researchers have developed remains uncertain. Modification of land and waterways in Europe|alt=Photograph from space showing deforestation in Europe Humans place high demand on land not only to build urban centers, but also to build surrounding suburban areas for housing. Land is also allocated for agriculture to sustain the growing population of the city. Expanding cities and suburban areas necessitate corresponding deforestation to meet the land-use and resource requirements of urbanization. Key examples of this are Deforestation in the United States and Europe. Along with manipulation of land to suit human needs, natural water resources such as rivers and streams are also modified in urban establishments. Modification can come in the form of dams, artificial canals, and even the reversal of rivers. Reversing the flow of the Chicago River is a major example of urban environmental modification. Urban areas in natural desert settings often bring in water from far areas to maintain the human population and will likely have effects on the local desert climate. Trade, shipping, and spread of invasive species |alt=A ship in the Firth of Clyde, potentially carrying invasive species , Atlanta|alt=Kudzu vines smothering trees in Atlanta Both local shipping and long-distance trade are required to meet the resource demands important in maintaining urban areas. Carbon dioxide emissions from the transport of goods also contribute to accumulating greenhouse gasses and nutrient deposits in the soil and air of urban environments. In addition, shipping facilitates the unintentional spread of living organisms, and introduces them to environments that they would not naturally inhabit. Introduced or alien species are populations of organisms living in a range in which they did not naturally evolve due to intentional or inadvertent human activity. Increased transportation between urban centers furthers the incidental movement of animal and plant species. Alien species often have no natural predators and pose a substantial threat to the dynamics of existing ecological populations in the environment into which they are introduced. Invasive species are successful when they are able to have proliferate reproduction due to short life cycles, contain or adapt to have traits that suit the environment and appear in high densities. Such invasive species are numerous and include house sparrows, ring-necked pheasants, European starlings, brown rats, Asian carp, American bullfrogs, emerald ash borer, kudzu vines, and zebra mussels among numerous others, most notably domesticated animals. Brown rats are a highly invasive species in urban environments, and are commonly seen in the streets and subways of New York City, where they pose multiple negative effects to infrastructure, native species and human health. Brown rats carry several types of parasites and pathogens that can possibly infect humans and other animals. In New York City a genetic study exploring genome wide variation concluded that multiple rats were originally from Great Britain. Also urban species can serve many more purposes including agriculture, transport, and protection. Negative effects Some urban species have a negative impact on humans. For example, pests' urine, fecal matter, and skin fragments can spread germs if ingested by humans. Diseases caused by pests or insects can be fatal. They include: salmonella, meningitis, Weil's disease, Lyme disease, etc. Some people are allergic to certain insects like bees, wasps and therefore being exposed to them will cause serious allergic responses (rashes for example). According to Seth Magle, attacks from wildlife in an urban setting, while rare are detrimental to societal views on wildlife. Due to media coverage of these rare attacks, urban populations assume these interactions as more common than they really are which further affects the tolerance of urban wildlife. Human effects on biogeochemical pathways Urbanization results in a large demand for chemical use by industry, construction, agriculture, and energy providing services. Such demands have a substantial impact on biogeochemical cycles, resulting in phenomena such as acid rain, eutrophication, and global warming. Demand for fertilizers to meet agricultural needs exerted by expanding urban centers can alter chemical composition of soil. Such effects often result in abnormally high concentrations of compounds including sulfur, phosphorus, nitrogen, and heavy metals. In addition, nitrogen and phosphorus used in fertilizers have caused severe problems in the form of agricultural runoff, which alters the concentration of these compounds in local rivers and streams, often resulting in adverse effects on native species. A well-known effect of agricultural runoff is the phenomenon of eutrophication. When the fertilizer chemicals from agricultural runoff reach the ocean, an algal bloom results, then rapidly dies off. The dead algae biomass is decomposed by bacteria that also consume large quantities of oxygen, which they obtain from the water, creating a "dead zone" without oxygen for fish or other organisms. A classic example is the dead zone in the Gulf of Mexico due to agricultural runoff into the Mississippi River. Just as pollutants and alterations in the biogeochemical cycle alter river and ocean ecosystems, they exert likewise effects in the air. Some stems from the accumulation of chemicals and pollution and often manifests in urban settings, which has a great impact on local plants and animals. Because urban centers are often considered point sources for pollution, local plants have adapted to withstand such conditions. == Urban effects on climate ==

Urban environments and outlying areas have been found to exhibit unique local temperatures, precipitation, and other characteristic activity due to a variety of factors such as pollution and altered geochemical cycles. Some examples of the urban effects on climate are urban heat island, oasis effect, greenhouse gases, and acid rain. This further stirs the debate as to whether urban areas should be considered a unique biome. Despite common trends among all urban centers, the surrounding local environment heavily influences much of the climate. One such example of regional differences can be seen through the urban heat island and oasis effect. Much of this effect can be attributed to low city albedo, the reflecting power of a surface, and the increased surface area of buildings to absorb solar radiation. In the 20th century, American climate scientist James E. Hansen concluded that Greenhouse effect is changing the climate for the worse. Ecosystems in and around the urban center are especially influenced by these point sources of pollution. High sulfur dioxide concentrations resulting from the industrial demands of urbanization cause rainwater to become more acidic. Such an effect has been found to have a significant influence on locally affected populations, especially in aquatic environments. which is characterized by the predominance of certain species and climate trends such as urban heat island across many urban areas. Examples of species characteristic of many urban environments include, cats, dogs, mosquitoes, rats, flies, and pigeons, which are all generalists. Many of these are dependent on human activity and have adapted accordingly to the niche created by urban centers. However, the large number of wild species being discovered in urban areas around the world suggest that a bewildering diversity of life is able to call urban areas their home. The relationship between urbanisation and wildlife diversity may not be as straightforward as previously imagined. This change in imagination has been possible due to coverage of a much larger number of cities in varied parts of the world that now show that past trends and assumptions were largely due to a bias in coverage of cities in temperate, developed countries. == Biodiversity and urbanization ==

Research in countries of temperate areas indicates that, on a small scale, urbanization often increases the biodiversity of non-native species while reducing that of native species. This normally results in an overall reduction in species richness and increase in total biomass and species abundance. Urbanization reduces diversity on a large scale in cities of developed countries, but in tropical and subtropical cities, despite the high human densities, can retain very high diversity if small patches of habitats are retained across the city. Even domestic urban and suburban properties near high density city centres can support well over a thousand macro-organism species, many of which are often native. These urban landscapes can also support many complex ecosystem interactions. Urban stream syndrome is a consistently observed trait of urbanization characterized by high nutrient and contaminant concentration, altered stream morphology, increased dominance of dominant species, and decreased biodiversity The two primary causes of urban stream syndrome are storm water runoff and wastewater treatment plant effluent. but these general trends do not apply to all organisms within those groups. For example, McKinney's (2006) Generalist species, those that use a wide range of resources and can thrive under a large range of living conditions, are likely to survive in uniform environments. Specialist species, those that use a narrow range of resources and can only cope with a narrow range of living conditions, are unlikely to cope with uniform environments. A study of 463 bird species reported that urban species share dietary traits. Specifically, urban species were larger, consumed more vertebrates and carrion, and fed more frequently on the ground or aerially, and also had broader diets than non‐urban species. Such changes reflect the process of synurbization, in which wildlife populations undergo adaptive shifts in response to urban environments. Cause of diversity change The urban environment can decrease diversity through habitat removal and species homogenization—the increasing similarity between two previously distinct biological communities. Habitat degradation and habitat fragmentation Although this replacement of suitable habitat with unsuitable habitat will result in extinctions of native species, some shelter may be artificially created and promote the survival of non-native species (e.g. house sparrow and house mice nests). Changes to the habitat may promote both the extinction of native endemic species and the introduction of non-native species. The effects of habitat change will likely be similar in all urban environments as urban environments are all built to cater to the needs of humans. In China, fish that were exposed to industrial wastewater had poorer body condition; being exposed to toxicants can increase susceptibility to infection. In 2025, several taxa were described from city environments, including the skink Scincella chengduensis and the shrub Euonymus chengduanus from forest remnants in Chengdu, China, the fish Cobitis beijingensis from highly human-altered streams in Beijing, China, the beetle Longitarsus cohongorooto from ruderal ecosystems in the greater Washington, DC region, Punctaltica (a new beetle genus) from a city park in Shenzhen, China, and the leafhopper genus Bamboosella described from several European cities. New species have also been described from heavily urbanized settings, including the spider Loxosceles tenochtitlan from houses in Mexico City, 42 new Megaselia fly species discovered in Los Angeles residential backyards (BioSCAN), the fly Drapetis bruscellensis from the outskirts of Brussels and supported by COI barcoding, and urban-associated taxa from São Paulo, Brazil, including three Mesabolivar spiders from leaf litter and two Drosophila species associated with plant inflorescences in the city. Urban species discovery also includes vertebrates, such as the leopard frog Rana kauffeldi described from New York City and surrounding Atlantic Coast regions, and Zakerana dhaka described from Dhaka, Bangladesh. Behavioural homogenization Urbanization can alter not only which species occur in cities, but also how they behave. Urban environments often favour a recurring suite of traits, sometimes referred to as an 'urban wildlife syndrome', including reduced fear of humans, greater use of anthropogenic food, shifts in daily activity, and increased use of human-made structures. Such repeated shifts may reduce behavioural diversity across individuals, populations, and species - a process termed 'behavioral homogenization' - potentially affecting ecosystem functioning, animal cultures, and human–wildlife interactions. == Ways to improve urban ecology: civil engineering and sustainability ==

Cities should be planned and constructed in such a way that minimizes the urban effects on the surrounding environment (urban heat island, precipitation, etc.) as well as optimizing ecological activity. For example, increasing the albedo, or reflective power, of surfaces in urban areas, can minimize urban heat island, resulting in a lower magnitude of the urban heat island effect in urban areas. By minimizing these abnormal temperature trends and others, ecological activity would likely be improved in the urban setting. Need for remediation taking place in Shibuya Urbanization has indeed had a profound effect on the environment, on both local and global scales. Difficulties in actively constructing habitat corridors and returning biogeochemical cycles to normal raise the question as to whether such goals are feasible. However, some groups are working to return areas of land affected by the urban landscape to a more natural state. This includes using landscape architecture to model natural systems and restore rivers to pre-urban states. Since the securing of land as a protected area is a luxury that cannot be extensively implemented, alternative approaches must be explored in order to prevent mass extinction of species. Borgström et al. 2006 hold that urban ecosystems are especially prone to "scale mismatch" whereby the right course of action is heavily dependent on species size. For some species conservation can be achieved in a single isolated garden because their small size permits a large population, e.g. soil microorganisms. Meanwhile, that is the wrong scale for species that are more mobile and/or larger, e.g. pollinators and seed dispersers, which will require larger and/or connected spaces. The need to pursue conservation outcomes in urban environments is most pronounced for species whose global distribution is contained within a human-modified landscape. The fact is that many threatened wildlife species are prevalent among land types that were not originally intended for conservation. • No predators capable of killing children will be reintroduced to urban areas. • There will be no introduction of species that significantly threaten human health, pets, crops or property. • Reintroduction will not be done when it implies significant suffering to the organisms being reintroduced, for example stress from capture or captivity. • Organisms that carry pathogens will not be reintroduced. • Organisms whose genes threaten the genetic pool of other organisms in the urban area will not be reintroduced. • Organisms will only be reintroduced when scientific data support a reasonable chance of long-term survival (if funds are insufficient for the long-term effort, reintroduction will not be attempted). • Reintroduced organisms will receive food supplementation and veterinary assistance as needed. • Reintroduction will be done in both experimental and control areas to produce reliable assessments (monitoring must continue afterwards to trigger interventions if necessary). • Reintroduction must be done in several places and repeated over several years to buffer for stochastic events. • People in the areas affected must participate in the decision process, and will receive education to make reintroduction sustainable (but final decisions must be based on objective information gathered according to scientific standards). Sustainability With the ever-increasing demands for resources necessitated by urbanization, recent campaigns to move toward sustainable energy and resource consumption, such as LEED certification of buildings, Energy Star certified appliances, and zero emission vehicles, have gained momentum. Sustainability reflects techniques and consumption ensuring reasonably low resource use as a component of urban ecology. Techniques such as carbon recapture may also be used to sequester carbon compounds produced in urban centers rather continually emitting more of the greenhouse gas. The use of other types of renewable energy like bioenergy, solar energy, geothermal energy, and wind energy would also help to reduce greenhouse gas emissions. Green Infrastructure Implementation Urban areas can be converted to areas that are more conducive to hosting wildlife through the application of green infrastructure. Although the opportunities of green infrastructure (GI) to benefit human populations have been recognized, there are also opportunities to conserve wildlife diversity. Green infrastructure has the potential to support wildlife robustness by providing a more suitable habitat than conventional, "grey" infrastructure as well as aid in stormwater management and air purification. GI can be defined as features that were engineered with natural elements or natural features. Increasing Wildlife Habitat Connectivity The implementation of wildlife corridors throughout urban areas (and in between wildlife areas) would promote wildlife habitat connectivity. Habitat connectivity is critical for ecosystem health and wildlife conservation yet is being compromised by increasing urbanization. Urban development has caused green spaces to become increasingly fragmented and has caused adverse effects in genetic variation within species, population abundance and species richness. Urban green spaces that are linked by ecosystem corridors have higher ecosystem health and resilience to global environmental change. In a study performed by Tempe Adams (et al.), remote-sensor camera traps and data from GPS collars were utilized to assess whether or not the African elephant would use narrow urban wildlife corridors. The study was performed in three different urban-dominated land use types (in Botswana, South Africa) over a span of two years. The results of the study indicated that elephants tended to move through unprotected areas more quickly, spending less time in those areas. Roadkill mortality has detrimental effects on the persistence probability, abundance and genetic diversity of wildlife populations (more so than reduced movement through habitat patches). Urban ecology follows western science frameworks and compartmentalizes nature. Urban ecology has the opportunity to be viewed in an interconnected and holistic way, through "Two-Eyed Seeing" and be inclusive of the Traditional Ecological Knowledge held by the local Indigenous Peoples of the area. Urban restoration ecology would be enriched by partnerships with the local Indigenous Peoples, if done in a respectful way that addresses the currently inequitable relationship. == Summary ==

Urbanization results in a series of both local and far-reaching effects on biodiversity, biogeochemical cycles, hydrology, and climate, among other stresses. Many of these effects are not fully understood, as urban ecology has only recently emerged as a scientific discipline and more research remains to be done. Research on cities outside the US and Europe remains limited. Observations on the impact of urbanization on biodiversity and species interactions are consistent across many studies but definitive mechanisms have yet to be established. Urban ecology constitutes an important and highly relevant subfield of ecology, and further study must be pursued to more fully understand the effects of human urban areas on the environment. == See also ==