By Jeremy Hance / Mongabay

In 48 years wildlife populations in the tropics, the region that holds the bulk of the world’s biodiversity, have fallen by an alarming 61 percent, according to the most recent update to the Living Planet Index. Produced by the World Wide Fund for Nature (WWF) and the Zoological Society of London (ZSL), the index currently tracks almost 10,000 populations of 2,688 vertebrate species (including mammals, birds, reptiles, amphibians, and fish) in both the tropics and temperate regions.

“Much as a stock market index measures the state of the market by tracking changes in […] a selection of companies, changes in abundance (i.e., the total number of individuals in a given population) across a selection of species can be used as one important indicator of the planet’s ecological condition,” the report reads.

Between 1970 to 2008, species abundance in the tropics fell by 44 percent on land, 62 percent in the oceans, and 70 percent in freshwater environments, culminating in an average loss of 1.25 percent every year since the baseline was set in 1970. Wildlife populations are declining due to a number of large-scale human impacts including ongoing deforestation, habitat degradation, overexploitation for food or medicine, pollution, agricultural, overfishing, invasive species, disease, climate change, dams, mining, and other industrial projects.