Urban expansion would endanger 855 species of animals

Cities could be the solution rather than the problem to the environmental issue, according to a new study by Yale University, published in the journal Proceedings of the National Academy of Sciences. The authors suggest that an urban planning approach that protects habitats could alleviate the impact on species.

Global urban expansion is expected to account for up to 1.53 million square kilometers of new urbanized land over the next three decades, which would be a direct threat to the survival of 855 species.

In 30 years, the world's urban population is estimated to grow to 2.5 billion people, making urbanization one of the defining transformations of the twenty-first century.

Urban land will need to expand to accommodate these new urban residents, a process that occurs followed at the expense of natural ecosystems. At a time when global biodiversity is seriously threatened, this represents a challenge to sustainable urban development.

Much of this expansion is therefore expected to occur in so-called “biodiversity hotspots”, which are the species-rich areas that are endangered by human activity. In this way, a wide variety of species would be at high risk of destruction, many of which are already threatened with extinction.

Cities can support diverse plant and animal communities, and access to nature is recognized as a key component in making cities functional and livable places for people.

However, when urban land replaces natural habitat, it permanently alters the type of habitat available, along with its spatial configuration and level of interconnection, which brings significant changes to the abundance and composition of species sets. Generally, the richness of native species decreases with the intensity of urban land use, and urban areas tend to host more invasive species, so the proportion of these usually increases with the degree of urbanization.

Urban land can also drive phenotypic adaptations, producing rapid eco-evolutionary change. These impacts on biota (the aggregate species of plants, animals and other organisms that occupy a given area) contribute to the decline in global biodiversity.

The cities that pose the greatest threat to species due to their expansion are mostly found in the developing tropical regions of sub-Saharan Africa, South America, Mesoamerica and Southeast Asia.

For researchers, global efforts should be focused on minimizing the impact on the habitats of these growing regions, which could help conserve and protect species classified as “threatened”, according to the Red List of the International Union for the Conservation of Nature (IUCN)

To carry out the study, they used a set of recent land use projections developed to assess future habitat loss resulting from urban expansion for more than 30,000 terrestrial species worldwide. It also showed that the expansion of urban land is an important factor in habitat loss for approximately one third of them.

They were also based on the Yale Map of Life, a collection of species distribution data used to monitor, research and create policies for the protection of species around the world. The study demonstrates the need for global conservation efforts to include policies to preserve urban land species.

The solution

“Cities are actually part of the solution,” explained Karen Seto, from the Yale School of the Environment and co-author of the study, “because we can build cities differently than we have done in the past. They can be good for the planet, they can save species, they can be centers of biodiversity, and they can save land for nature.”

The greatest impacts come from urban areas whose expansion can destroy habitats and have a large number of endemic species. One of the objectives of the study was to identify those species, not only threatened, but those specifically threatened by this development of urban land.

Economic pressures, governance structures, biodiversity conservation and awareness of the importance of protecting habitats are among the major obstacles to containing the problems that come with urban expansion.

In areas from central Mexico to Central America, the Caribbean, Haiti, Nigeria, Cameroon, Sri Lanka, Indonesia, Malaysia, Thailand, Brazil and Ecuador, species under the greatest pressure for expansion are concentrated.

“This study is important because it allows us to calculate which specific species are most threatened by urban growth and where urban protected areas are needed to safeguard them,” explained Robert McDonald, scientist at The Nature Conservancy Foundation.

Most of the planned places of urban expansion were not built for the time being, so “science-driven policies that guide how the cities of tomorrow are built will have a tremendous effect” on species, Seto concluded.

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