Animals are crucial to reforestation, research finds.
And yet, the world’s wildlife populations have declined by almost 70% in the last 50 years as humans have destroyed and polluted habitats.
Efforts to restore forests have often focused on trees, but a new study in the journal Philosophical Transactions that animals play a key role in the recovery of tree species by carrying a wide variety of seeds into previously deforested areas.
Sergio Estrada-Villegas, a postdoctoral associate at the Yale School of the Environment, led the study with Liza Comita, professor of tropical forest ecology. The project examines a series of regenerating forests in central Panama spanning 20 to 100 years post-abandonment.
“When we talk about forest restoration, people typically think about going out and digging holes and planting seedlings,” Comita says. “That’s actually not a very cost-effective or efficient way to restore natural forests. If you have a nearby preserved intact forest, plus you have your animal seed dispersers around, you can get natural regeneration, which is a less costly and labor-intensive approach.”
The research team analyzed a unique, long-term data set from the forest in Barro Colorado Nature Monument in Panama, which the Smithsonian Tropical Research Institute oversees, to compare what proportion of tree species in forests were dispersed by animals or other methods, like wind or gravity, and how that changes over time as the forest ages. The team focused on the proportion of plants dispersed by four groups of animals: flightless mammals, large birds, small birds, and bats.
Because the area has been intensely studied by biologists at the Smithsonian for about a century, the research team was able to delve into data stemming back decades, including aerial photographs taken in the 1940s-1950s. The area also presents a unique view into forests where there is very little hunting or logging. The results offer the most detailed data of animal seed dispersal across the longest time frame of natural restoration, according to the study.
The role of flightless animals in seed dispersal across all forest ages, from 20 years to old growth, and the variety of animal species involved were among the most important findings of the study and point to the importance of natural regeneration of forests, Comita and Estrada-Villegas say. In tropical forests, more than 80% of tree species can be dispersed by animals.
The researchers say the findings can serve as a road map for natural regeneration of forests that preserve biodiversity and capture and store carbon at a time when the UN Decade of Restoration is highlighting the need for land conservation, and world leaders are working to mitigate climate change stemming from fossil fuel emissions.
Forests soak up carbon dioxide from the atmosphere and store it in biomass and soils. Tropical forests, in particular, play an important role in regulating global climate and supporting high plant and animal diversity, the researchers note.
Estrada-Villegas, an ecologist who studies both bats and plants, says the study highlights how crucial animals are to healthy forests.
“In these tropical environments, animals are paramount to a speedy recovery of forests,” says Estrada-Villegas.
Coauthors are from the Max Planck Institute for Animal Behavior; the Universidad de los Andes in Bogota, Columbia; the Smithsonian Tropical Research Institute in Balboa, Panama; and Clemson University.
Source: Yale University