- New research looking at whether particular types of wildlife are more affected than others by habitat loss determined that predators are the most impacted, as was expected — but the study results held some surprises nonetheless.
- Because the loss of plant resources makes it harder for large predators to find sufficient food when land use changes occur within their range, researchers expected to find that these types of animals would be especially affected.
- The analysis showed that predators are indeed more affected by habitat loss than other groups — but that larger carnivores are not threatened with the largest declines. It was small invertebrates that were found to face the worst impacts.
New research looking at whether particular types of wildlife are more affected than others by habitat loss determined that predators are the most impacted, as was expected — but the study results held some surprises nonetheless.
The research team, led by Tim Newbold of University College London (UCL), set out to determine whether or not populations of carnivores and large-bodied animals suffered greater declines than other groups of animals when their habitats are lost due to human endeavors like urbanization or conversion of land to agriculture. Because the loss of plant resources makes it harder for large predators to find sufficient food when land use changes occur within their range, the researchers expected to find that these types of animals would be especially affected.
To test their prediction, Newbold and team used a database containing over one million records of the abundance of more than 25,000 species in natural habitats, such as primary forest, and human-disturbed habitats, from intensely managed farmlands to cities, in 80 countries around the world. After sorting animals into groups based on their size, whether they are warm- or cold-blooded, and whether they are carnivores, herbivores, or omnivores, the researchers analyzed the data to determine if large carnivores generally do drop in number more precipitously than other animals when their habitats are degraded or destroyed.
The analysis showed that predators are indeed more affected by habitat loss than other groups — but that larger carnivores are not threatened with the largest declines. It was small invertebrates that were found to face the worst impacts. The study’s results are detailed in a study published in the journal Functional Ecology.
“Normally when we think of predators, we think of big animals like lions or tigers. These large predators did not decline as much as we expected with habitat loss, which we think may be because they have already declined because of human actions in the past (such as hunting),” Newbold said in a statement. “We find small predators — such as spiders and ladybirds — to show the biggest declines.”
Also disproportionately affected by habitat conversion, according to the study, were cold-blooded animals such as invertebrates, reptiles, and amphibians (small ectotherms); mammals and birds (large endotherms); and animals that eat fungi (fungivores). All of these groups saw their numbers reduced between 25% and 50% in disturbed lands compared to populations in natural habitats.
These findings are important, the researchers note, because ecosystems require a balance of different animal types to function properly, and, by driving disproportionate losses at the top of the food chain, habitat destruction appears to be disrupting that balance.
“The results, suggesting that certain functional groups are consistently favoured over others in land used by humans, imply a substantial restructuring of ecological communities,” the researchers write in the study. “Given that different functional groups make unique contributions to ecological processes, it is likely that there will be substantial impacts on the functioning of ecosystems.”
Newbold cautioned that the study was limited by the available data, which he and his co-authors found to be biased in some key ways. For instance, large parts of Asia remain under-sampled for several groups of animals, while birds are best represented among vertebrates and insects best represented among invertebrates.
“As with all global studies, we are limited in the information that is available to us about where animals are found and what they eat,” he said. “We were able to get information for more animals than ever before, but this was still only around 1 out of every 100 animals known to science.”
CITATION
• Newbold, T., Bentley, L. F., Hill, S. L., Edgar, M. J., Horton, M., Su, G., … & Purvis, A. (2020). Global effects of land use on biodiversity differ among functional groups. Functional Ecology. doi:10.1111/1365-2435.13500
