Drivers and impacts of global seed disperser decline

Professor Mauro Galetti, CBioClima Dissemination Coordinator, had an article published in the journal Nature Reviews Biodiversity in May, together with other researchers, on the need to include frugivores in conservation strategies, forest recovery and climate change mitigation. The article was the subject of an article by Agência FAPESP, which was also published in the June 10 edition of the Folha de São Paulo newspaper. The work is a relevant contribution to actions aimed at recovering ecosystems and mitigating the effects of climate change.

See the article below and here, here and here.

The fruit seed passes through the digestive tract of the dispersing animal, where it receives a treatment that makes it ready to germinate when deposited. (photo: Mauro Galetti/CBioClima)

Most plant species rely on animals for the dispersal of their seeds, and seed dispersal is the most widespread mutualistic ecosystem function provided by terrestrial vertebrates. Because seed dispersal affects plant gene flow, fitness and distributions, seed-dispersing animals influence ecosystem biodiversity, functioning and resilience to environmental changes. In this Review, we evaluate the decline of seed dispersers and the consequences for biodiversity and ecosystem functioning, including their maintenance, recovery and future trajectories under land-use change, wildfire, biotic invasions and climate change. Human-driven changes (habitat loss, landscape fragmentation, invasive species and direct exploitation of animals) have reduced the species diversity, trait diversity, abundance and movement of seed dispersers. These changes lead to declines in seed dispersal function along gradients of anthropogenic impact. Field studies and process-based models that evaluate resulting impacts on plant communities indicate pervasive negative consequences ranging from plant biodiversity decline to reduced carbon storage, with ongoing research seeking to quantify the magnitude of these effects and their impacts on human wellbeing. Addressing seed disperser decline represents an important pathway by which protection and restoration of animal biodiversity can support biodiversity, connectivity and functioning of vegetation communities, thus confronting the joint challenges of biodiversity loss and climate change.

Key points

Seed disperser decline sits at the intersection of biodiversity loss, land-use change and climate change, weakening nature’s ability to recover from disturbance, adapt to climate shifts and store carbon.

Similar to pollinator decline, seed disperser decline causes the disruption of plant–animal mutualisms. Most prominent impacts of pollination decline are economic and accrue over short time spans, whereas seed disperser decline threatens ecosystem functioning and resilience over longer time spans and larger spatial scales.

Ecosystem restoration and protection efforts risk failure to meet climate and biodiversity goals if seed disperser decline is left unmitigated. Targeted ecological restoration and refaunation to recover seed dispersal function can assist recovery of degraded landscapes and enhance ecosystem resilience.

The economic costs of seed disperser decline — such as lost carbon storage, reduced forest product provisioning and declining natural resilience to extreme environmental events — are probably large, but the scope of these costs globally is yet to be quantified.