Tropical Forests Unable to Recover Without Red-Legged Honeycreeper, Other Fruit-Eating Birds

Tropical forests are severely affected by fragmentation as human settlement, agriculture, and infrastructure, including roads, continue to expand, as observed since the Industrial Revolution.

As seen over the decades, wildlife biodiversity has been impacted by deforestation and habitat loss in remote forests across the tropics that were once untouched by human civilization. Amid forest fragmentation, these terrestrial environments are constantly damaged or destroyed.

This ecological disaster is further aggravated without the presence of frugivores or fruit-eating animals; which help trees and other types of plants to spread their seed and expand.

These findings are based on a new study led by the public research university ETH Zurich in Switzerland and other institutions worldwide. Researchers observed that frugivores enhance forest regeneration in fragment landscapes.

Tropical Forests in Danger

For the past century, swathes of forest lands have been fragmented due to multiple natural factors such as climate change and human-induced activities, including excessive logging, mining, and land use.

Although forest ecosystems are known for their resilience, scientists assert they still need help from frugivores, including fruit-eating birds such as the red-legged honeycreeper, palm tanager, and the rufous-bellied thrush.

In the study published in the journal Nature Climate Change on Monday, April 15, an international team of researchers warned that tropical forests are in potential danger. One of the main reasons for this predicament is that they cannot recover naturally without fruit-eating birds.

The findings are based from ETH Zurich's Crowther Lab which showed this critical barrier to natural forest restoration, which is assured through seed dispersal.

In relation to the study, persistent deforestation and habitat loss in the tropical region could force not only fruit-eating birds but also other frugivores like orangutans and bats to migrate. Potential movement of these in long distances could leave forests exposed and without any agents for their seeds to spread.

Forest Restoration

The new research paper comes under the context that forest restoration is an important process when it comes to fighting biodiversity crises and climate change.

In addition, the researchers highlight the current challenges in representing animals in restoration and climate change policies; this is because the quantitative data on their contribution to forest regeneration and carbon recovery is still lacking.

In the study, the research team used individual-based models to examine frugivore-influenced seed rain in open areas within fragmented tropical forests. They found the movement of large birds was limited in terrestrial areas with less than 40% forest cover.

Meanwhile, small birds continue to disperse seeds and contribute to the recovery of tropical forests.

Using the forest landscapes in the Atlantic side of Brazil, the team showed that even wild tropical birds move freely across this habitat.

This process potentially increases the carbon storage of trees undergoing forest restoration by up to 38%, as cited by the AAAS during its media release on Monday.