nsisting almost entirely of closely-related rodents would be considered far less diverse than another that was home to a wide genetic range of rodents, marsupials, and more—even if the two patches of land had the same number of species.
By applying these approaches to data on all known small mammal species and all those species' characteristics, scientists are able to see the forest from the trees, uncovering patterns they wouldn't have using any single dimension of diversity alone.
This is how de la Sancha and his co-authors found, based on functional and phylogenetic measures, that while deforestation causes local extinctions, climate-related variables had more of an effect on small mammal biodiversity patterns across the entire forest system.
In other words, if a section of rainforest was cut down, some of the animals living there might disappear from that area, while the same species living in intact patches of rainforest could survive. And, the researchers found, even if a species disappears from one area, different species that play a similar role in the ecosystem tend to replace them in other forest patches and other parts of the forest system. Meanwhile, changes to the climate may have big, sweeping effects on a whole rainforest system. This study found that BIO9, a bioclimatic variable measuring mean temperature of the driest quarter—more simply put, how hot the forest is in its least rainy season—affects biodiversity across the whole forest system.
Knowing these climate variables play a role in rainforest health can be concerning. This study and others provide strong evidence of climate change's effects on large ecosystems, underlining the urgency of studying and protecting habitats like the Atlantic Forest, the South American forest system at the center of the study.
"We still have so much that we don't know about so many of these species, which underlines the necessity for more fieldwork," de la Sancha says. "Once we have more specimens, we can improve how we quantify functional diversity and our understanding of why these small mammals evolved the way they did. From there, we can keep better track of biodiversity in these areas, leading to improved models and conservation strategies down the line."
Still, with only 9-16 percent of the Atlantic Forest's original habitat space remaining, this study lends a silver lining to an otherwise grim narrative about the effects of human activity on rainforests.
"I think this gives us a little bit of hope. As long as we have forest—and we need to have forest still—we can maintain biodiversity on a large scale," de la Sancha says. "As long as we don't wipe it all out, there's good evidence to show that we can maintain biodiversity, at least for small mammals, and the ecosystem services these critters provide."