Human Pressure On Wild Animal Habitats
Species extinction has been a growing concern for much of the 20th and 21st centuries, with advocates, NGOs, governments, and individuals recognizing the problem and acting to reduce it. Many different factors cause animal populations to decline, including human disturbances. Indeed, human-made infrastructure like farmland, roads, and buildings invade wild animals’ habitats.
In this study, an international group of scientists explored the extent of the issue by mapping the home ranges of 20,000 land animals onto estimates of human activities that are known to alter natural ecosystems. This includes built environments (buildings and parks), electricity grids, farmland, roads, railways, navigable waterways (rivers and lakes), and human population densities. Based on their impact on the environment, these “pressures” were given a standardized score between zero to 50. Zero represents wilderness areas that are absent of human activities. A score of 3 or above is when land-use starts to become inaccessible to wildlife. Only areas where human pressures obtained a score of 3 or greater were included in the study, to asses their impact on animals’ home ranges.
The study reported three major findings. First, 85% of the species analyzed (including, broadly, mammals, birds, reptiles, and amphibians) had more than half of their habitat under intense human activity. Second, this statistic was higher if the species were classified as being ‘threatened’ (animals that are close to extinction) and if they had a habitat size equal to or less than South Korea (100,000 km2). Thirdly, the number of species affected by human activities increased by 44% from 1993 to 2009.
While this study highlights how humans have become “invasive” as a species in our own way, the authors acknowledge that some species can survive in some urban areas under human pressures. However, their survival comes with consequences – they reproduce less and their behavior drastically changes. One limitation of this study is that it didn’t consider other human-driven factors like climate change, overharvesting, and diseases. Nonetheless, the study focused on human’s impact on wild animal range size, which is key to understanding species extinction.
What can animal advocates do with this knowledge? Habitats needing restoring (if under human activity) and those needing protection (if free from human pressure) can be identified easily using this technique. Once identified, conservationists can prioritize species at risk of habitat loss and subsequent species decline. As echoed by the authors, “Given the growing human influence on the planet, time and space are running out for biodiversity, and we need to prioritize actions against these intense human pressures.”