Can Human Infrastructure Improve Biodiversity?

Go outside and look up. What do you see? You probably see clouds, maybe some tree branches providing shade, and you may also see electrical lines criss-crossing across the sky and emitting a soft hum as they deliver electricity to us. These are man made structures constructed to benefit humans, who have a history of degrading land for their own benefit. But what if these structures could benefit other animals? That is a question asked by Miguel Ferrer and his colleagues in Sevilla, Spain. 

Wildlife corridors are often used to connect fragmented habitats. One example is green bridges over highways to safely move animals across the pavement without risking the lives of the animals or humans. As habitats become increasingly fragmented due to human land use and climate change, researchers are looking for innovative ways to safely move animals through the patchwork of wild and man-made habitats while also increasing biodiversity. Some researchers have created small patches of habitat in an uninhabitable landscape which allows organisms to jump from safe patch to safe patch. For Ferrer and his team, the solution may be electrical lines. 

Electrical lines cut through human civilization and deliver power to the cities and to rural communities, connecting populations of humans. These lines move through a variety of habitats and may connect a forest on one side of the city to another forest on the other side. Ferrer and his colleagues saw electrical lines as ready-made wildlife corridors, just waiting to be exploited.

The researchers chose two 27 kilometer segments of power lines in southern Spain and modified the habitat at the base of six transmission towers (the tall structures that hold the electrical lines). They only modified the base of the towers in order to maintain the farming people were doing directly under the elevated electrical line. Beneath each tower they created refuges for small mammals and invertebrates using stones and planted seedlings of native shrub species. They also included two unmodified control plots used to compare the results to. At each modified transmission tower and the controls they counted the number of invertebrates, small mammals, and birds for four years. 

Electric Towers are Effective Wildlife Refuges 

One year after modifying the electrical towers, the researchers found ten times more small mammals, four times more arthropods, and nearly eight times more birds than the unmodified towers! The modified towers also had a greater number of species. For example, the unmodified towers hosted fewer birds with many species only occurring near the modified towers. 

For all three organism groups (mammals, arthropods, and birds) the number of observed species peaked during the first year of the study and plateaued at that number for the duration of the study. This means that within one year, the electrical towers attracted their maximum capacity and were able to sustain the large population and diversity for many years. Increasing the size of the modification or increasing the number of modified electrical towers may increase the biodiversity even more!

The tower modification also provides many ecosystem services to the surrounding humans. A more diverse arthropod community means there are more organisms to disperse seeds and pollinate which improves the surrounding ecosystems and farmland. Additionally, spreading seeds and pollen between the electrical tower refuges could facilitate more connectivity between these fragmented habitats. 

Different types of modifications can improve habitat for different types of animals. In this experiment the rocks and native plants attracted small mammals and arthropods which then attracted birds. Another modification with a water feature may attract amphibians or more plants may attract a diversity of pollinators. Furthermore, this electrical tower modification is an affordable restoration option, at only 450 euros per tower (about 545 USD) and no maintenance costs after installation. Additionally, not every tower needs to be modified. These towers should act as a corridor to ferry animals through fragmented landscapes meaning only those in currently fragmented habitats need to be modified. 

This is a novel study that transforms human infrastructure that creates fragmented landscapes into a tool to prevent fragmentation. Humans are part of the natural ecosystem and there are ways to make our way of life work for other organisms in the ecosystem. This study uses electrical towers to modify and connect fragmented landscapes on the kilometer scale. But we can see similar fragmentation corridors in our own neighborhoods. Pollinator gardens allow bees and other pollinators to navigate across the concrete jungle to find enough sustenance. Parks and urban trees provide nesting habitat for birds. Habitat fragmentation, and ultimately habitat loss, is one of the leading causes of biodiversity decline and creating patches of suitable habitat and corridors between fragments is one small way we can make a huge difference in combating biodiversity loss. 

Source: Ferrer M, De Lucas, M, Hinojosa, E. and Morandini, V. 2020. Transporting Biodiversity Using Power Lines as Stepping-Stones? Diversity 12(11) 439. https://doi.org/10.3390/d12110439