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Humans are causing evolution of several species Metro investigates how the growing worldwide urbanization causes dramatic environmental changes that put pressure on species and make them adapt or disappear. DANIEL CASILLAS
Metro World News
Human populations are moving massively into cities, causing a rapid increase and extension of urban areas. These changes are causing declines in the numbers of many species. However, our activities may also pressure some of them to adapt and evolve. That can sometimes occur very quickly, as it was revealed by the investigation dubbed ‘Evolution of life in urban environments,’ recently published in the journal Science. Urbanization is a phenomenon that has become more relevant recently and is expected to worsen in the future. According to the data by The United Nations Population Fund (UNFPA), more than half of the world’s population now lives in towns and cities, and by 2030 this number will swell to around 5 billion. As the world continues to urbanize, humanity is expected to face several major problems, such as a greater concentration of poverty, overpopulation and increased difficulties in accessing natural resources. But the growing urbanization of the world does not only affect humans, it also impacts and affects animal species that inhabit cities or their surroundings. That situation pushes them to adapt to the new environment, even through evolutionary changes that occur between one generation and the next.
“Urbanization process could lead to a loss of endemic species in the area due to the appearance of invasive or other species. Eventually local urban fauna could loose identity” Amparo Herrera-Dueñas, expert on the effect of urbanization on biodiversity at the Complutense University of Madrid, Spain
“The increasing urbanization of the territory will affect in a positive or negative way the species of the zone according to the range of tolerance that these show to the presence of the human being and its way of life. For some species, urban areas are thus a source
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species that have evolved in urban environments |PHOTOS: CREATIVE COMMONS
of opportunities for the colonization and exploitation of their resources, while for others, urbanization of the territory entails a decline in their populations and even their disappearance from the urbanized area,” Amparo Herrera-Dueñas, expert on the effect of urbanization on biodiversity at the Complutense University of Madrid, Spain, explained to Metro. ‘Evolution of life in urban environments’ by biology professors Marc Johnson, of University of Toronto, and Jason Munshi-South, of Fordham University in New York, documents over 100 cases of populations evolving in response to pressures exerted by humans. “Urbanization has affected major evolutionary proces- ses for many populations of plants, animals, and microbes. In our paper, we document over 100 cases of populations evolving in response to pres- sures exerted by cities. These evolutionary responses inclu- de random changes that build up from one generation to the next,” Jason Munshi-South, associate professor at the Fordham
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Q&A
KIRSTEN PARRIS,
associate professor at The University of Melbourne, Australia, and author of the book ‘Ecology of Urban Environments’ Uditene vent
How has the extension of urban areas affected animals? Cities around the world have reduced the amount of habitat available for species other than humans. This trend is accelerating with the increased pace of urbanization globally. However, cities are often built in areas that are naturally high in biodiversity, and they still support many native species – including endangered species. For example, 376 federally-listed threatened species in Australia (30 per cent of the total) are known to live in cities around the country (with a city defined as a settlement with 10k or more people).
University, U.S. and co- author of the study told Metro. According to the research this divergent selection has led to adaptive evolution in life history, morphology, physiology, behavior, and reproductive traits. These adaptations typically evolve in response to pesticide use, pollution, local climate, or the physical structure of cities. Thus, species affected by urbanization can evolve and generate changes that will allow new generations to have better tools to face the environment, such as different or longer peaks in the case of birds or immunity to pesticides, in the case of some insects. “Those that adapt have adequate variation in traits of interest for natural selection to act on. Thus, descendants in each generation will be more likely to carry traits that are better adapted to the urban environment,” Munshi-South added. “And such adaptations could be the difference as to whether a species persists or vanishes from urban areas.” But evolution in urban environments can also pose some threats to species and the environment in general even directly to humans. Because some species may lose genetic variation, while pests
What kind of environmental changes does urbanization cause? Urbanization causes dramatic environmental changes, including the replacement of vegetation and soft ground with hard surfaces that are impermeable to water (such as pavements and the roofs of buildings); the loss of open space; the isolation of small areas of habitat by roads and other infrastructure; the loss or modification of wetlands and streams; pollution of air, water and soil; increased noise and artificial light at night; and climatic changes (particularly increased temperatures resulting from the urban heat-island effect). Cities can be viewed as habitats for people, but all these environmental
can become more resistant and cause health problems among humans. “Species that successfully adapt, particularly pests or invasive species, may then spread and cause economic and public health issues for human populations”, the coauthor of the research stated. To avoid these dangers and reduce the impact on animal species, experts advise looking for better ways to share urban environments. “We need to think harder about how we – as urbandwelling humans – can better share the urban landscape
changes combined can make life very difficult for other species. How do species adapt to urbanization? Some species have shown remarkable adaptations to urban living. While cities can be very different environments from the ones they replace, they can also provide key resources for wildlife such as shelter, food and breeding sites. Animals that can take advantage of these resources can thrive in cities. For example, the southern brown tree frog in Melbourne, Australia lives in ponds in city parklands on the fringe of the CBD. This frog has large, sticky toes which allow it to climb up and down the vertical walls that often surround these ornamental ponds, and has maintained populations for many decades where other species of frogs have died out. Songbirds that rely on sound to communicate with each have shown a range of adaptations to background noise in cities, singing higher, louder and later at night so they can be better heard by other birds. Recent research argues that urbanization can influence the evolution of some species… Yes, urbanization can influence evolution, because certain aspects of the urban environment are exerting strong selection pressure on the species that live there. What threats could it impose to the species and ecosystem? Urbanization can lead to the loss of populations and entire species, but it also may lead to the evolution of new lineages (possibly including new species). Urbanization is a threat to biodiversity, but the paradox is that urban areas can also provide important habitat for biodiversity and opportunities for conservation where people live and work.
with other species,” Kirsten Parris, associate professor at The University of Melbourne, Australia, and author of the book ‘Ecology of Urban Environments,’ concluded. “We can work to conserve the native animals and plants that still live in urban areas, and also to bring back some of those that have been lost. This obviously will benefit biodiver- sity but will also have many be- nefits for the billions of people who live in cities; maintaining a connection to nature is very important for human health, both physical and mental,” she added.
Peppered moths Killifish
Anolis
House finch
A small killifish that lives in many waterways of the northeastern U.S. has repeatedly evolved genetic resistance to a pollutant called PCBs.
In Puerto Rico, lizards called Anolis have evolved longer limbs and more of a particular type of scale that allows them to move along walls better than before. Prior to urbanization they lived primarily on trees and bushes.
House finch, belonging to an urban population of this species in the city of Tucson, Arizona, have developed a longer, deeper and stronger bill than those from a nearby rural population in the Saguaro Desert.
The white-and-black-speckled wings of peppered moths once helped them blend in with similarly colored trees. But as the Industrial Revolution covered those trees with soot, some individuals of this species mutated to have black wings, which helped them survive and pass their genes on to the next generation.