The rainforest of Lopé National Park in central Gabon is one of the last safe havens for the endangered forest elephant (Loxodonta cyclotis). But in a new study in Science, researchers warn that elephants and other keystone species in the park, such as western lowland gorillas, chimpanzees, and mandrills, could be facing famine.
Climate change is disrupting the yield of fruit trees, a critical food source for many larger mammals. Scientists from Gabon’s national parks agency (ANPN) and the University of Stirling in Scotland, found a staggering 81% decline in fruit production in the protected area between 1986 and 2018.
Their analysis of an extensive photographic database covering a twenty-year period showed a critical decline in weight and body fat of forest elephants. An 11% decline in the body condition of forest elephants since 2008 is primarily attributed to decreased fruit consumption.
The researchers draw on a rare longitudinal data set funded by the EU’s ECOFAC-6 programme and collected by the ANPN. Every month for 34 years, botanists observed the crowns of more than 2,000 tropical trees and scanned the canopy for flowers, leaves, and both ripe and unripe fruits of 73 species important to the diet of elephants, gorillas and chimpanzees.
“The changes are drastic,” says Emma Bush, co-lead author of the study. “The massive collapse in fruiting may be due to missing the environmental cue to bear fruit.” Some tropical trees depend on a drop in temperature to trigger flowering, but since the 1980s, the region recorded less rainfall and a temperature increase of 1°C.
“Less fruit in the ecosystem will have huge impacts on rainforest dynamics such as seed dispersal, plant reproduction and food availability for wildlife,” says the conservation scientist. Where 30 years ago, an elephant would have found ripe fruits on almost one in every ten trees, today it needs to search more than 50 trees.
“Central Gabon’s forests are undergoing rapid, ecosystem-wide change,” says Aurélie Flore Koumba Pambo, scientific advisor to the National Park Authority. Over time, she says, reduced fruiting will impact on the forest structure and tree diversity, and this could further affect local and global climate.