A pair of pigeons on a grey street.

Pigeons are one of the animals that always benefit from humans using land for towns and cities. Image: Shutterstock.com.

Towns and cities benefit the same animals and plants everywhere

Human habitat modifications are favouring the same species everywhere, while unique species are disappearing, according to a new paper.

Man-made changes to habitats generally have a negative effect on the plants and animals living there - but not all species are affected equally by land use.

A study, published in PLOS Biology, was led by Dr Tim Newbold, a research fellow at University College London (UCL), and Prof Andy Purvis, a research leader at the Museum.

It used data from 81 countries to show that when humans modify natural habitats through farming, forestry or building, animals and plants that are unique to particular locations decline, replaced by those common to many places.

For instance, pigeons and rats benefit from cities and farms all over the world.

Researchers studied the area inhabited by nearly 20,000 different species of animals and plants. They showed that species already occupying a large area increased in places where humans use the land, while species occupying a small area are more likely to be lost.

Crucially, this pattern was seen in every kind of human land use - not just arable farms or urban areas, but also pastures, plantation forest and even land that is recovering from human use.

This means that human actions are favouring the same species everywhere, while the many species that are unique to specific places are disappearing.

The findings suggest a disruption to the healthy functioning of ecosystems, which support our natural environment and are critical in our efforts to grow food.

Prof Andy Purvis says, 'What is happening to biodiversity is similar to what is happening to high streets in British towns and cities. As small, independent retailers are going out of business, large chains dominate. It makes all towns look the same, and it's less easy to tell where you are.

'Likewise, people are affecting nature everywhere they go, and everywhere there are localised species which are struggling to make a living.'

Skyscapers in Hong Kong

Town, cities, farms and plantations are changing the way animals can use land. Image: Skyscapers in Hong Kong, Shutterstock.com.

 

A man-made problem

The researchers mapped the way humans use land and how it has changed over many centuries.

Many scientists argue that Earth has entered a new geological epoch called the Anthropocene, a period in which human activity is the biggest influence on the natural environment. Land use is one of the leading pressures on biodiversity, as humans change forests, woodlands and grasslands into towns, cities and farms.

These changes often hinder biodiversity, and the results of this study are worrying.

Plants and animals that live only on small areas of land are already at higher risk of extinction than species which have adapted to live all over the world. When humans disturb those small habitats, it can push organisms even closer to the brink of extinction.

It all adds up to a global reduction in biodiversity. Furthermore, species that live in small areas tend to need a very specific climate, making them more sensitive to climate change.

Dr Tim Newbold says, 'As humans, we place great value on animals and plants that are confined to particular locations. We travel around the world to see animals like tigers in Asia or rhinoceroses in Africa, and animals and plants are often our national emblems.

'We show around the world that when humans modify habitats, these unique species are consistently lost.'

Species living in tropical parts of the world were more adversely affected by land-use changes than ones living in cooler, temperate areas. This may be because tropical animals and plants usually have smaller ranges, and they are usually more specialised. Temperate regions also have a longer history of human disturbance, which may have already filtered out and killed the most sensitive species.

The data

Five hundred researchers contributed data to this study, including scientists from UCL, the Natural History Museum, the United Nations Environment World Conservation Monitoring Centre, the University of Sussex, the University of Colorado, China Agricultural University and the German Centre for Integrative Biodiversity Research.

The combined dataset was made up of 1.1 million records from 445 scientific surveys all over the world.

It is part of the PREDICTS project, a global database of terrestrial species' responses to human pressures.

Andy says, 'It is helpful to have a dataset that is so extensive, and that covers so many taxonomic groups, because we want to know what is happening globally.

'A lot of what we know about the state of nature, we know from a very small number of taxonomic groups. But looking at the best-known groups might not give you an accurate picture of what is happening to biodiversity across the world as a whole.'

What's next?

In the future, the team will be investigating how climate change may add to the losses of unique species.

The findings of this paper, and the PREDICTS project as a whole, will impact efforts to conserve the world's biodiversity.

Andy says, 'This dataset can inform us about nature and the planet in unprecedented ways. The benefit of matching biodiversity data with data about humans is that we can predict the different consequences of what humanity chooses to do next.

'Teams of research groups are trying to test whether it is possible to change the course of biodiversity loss, and what policies we need to implement to do that.'