The main finding from the research, which is based on 1,600 cases around the world, is that evolutionary changes, as a result of over half the world’s population now living in urban areas, could affect ecosystem services important to humans. The cases relates to tests on plants an animals where adaptations have taken place, including alterations in body sizes, shifts in behavioral patterns and adjustments in reproduction.
For example, the seeds of the plant hawksbeard (Crepis sancta) have become larger in order to adapt to urban areas. The reason is, the researchers speculate, is because heavier seeds are not carried far from a plant in the wind and tend to fall on nearby soil, whereas lighter seeds are carried further but would tend to fall on concrete or tarmac and are thus unable to germinate. Therefore, natural selection dictates that larger and heavier seeds have a greater chance of germinating within the urban environment.
Other examples are:
Human-caused global warming is prompting the seasonal onset of reproduction to occur earlier in 65 species of migratory birds in Western Europe.
The use of galvanized (zinc-coated) transmission towers creates “novel habitats” characterized by high zinc tolerance in multiple plant species.
The size of brown trout is being affected by fish ladders, which subsequently affects predators and prey.
Interviewed by the BBC, lead researcher Professor Marina Alberti, who works at the University of Washington’s Department of – Urban Design and Planning, said: “We found that there is a clear urban signal of big change, and also greater – physical and biochemical – change in urbanising systems compared to natural or non-urban anthropogenic systems.” The impact on humans arises from changes to biodiversity, which could seem some species disappear, and also with nutrient cycling, seed dispersal (which will affect agriculture) and water purification.
The speed of the adaptations have surprised the researchers. The findings fit with the proposal that the planet is entering an Anthropocene epoch. This is a geological measurement of time dating from when human activities started to have a significant global impact on Earth’s geology and ecosystems.
The research has been published in the journal Proceedings of the National Academy of Sciences. The paper is titled “Global urban signatures of phenotypic change in animal and plant populations.”
