Research finds that healthy, robust seabird populations play a key role in the resiliency of coral reefs and point to invasive species removal as an important method for restoring marine ecosystems. 

Throughout humanity’s exploration of Earth, we have consistently transported invasive species around the world, such as invasive rats to island ecosystems. Invasive rats quickly reproduce and spread all over the island in an ecosystem that has evolved in their absence. Native seabirds are left completely defenseless and suffer due to the predation of eggs, chicks, and competition for resources. The direct effects of this in the decline of the seabird population are clear, but there are also indirect effects on coral reefs and the surrounding marine ecosystems.

The presence and constant aggravations by invasive rats reduce native seabird populations and alter the distribution of nutrients across island ecosystem. Coral reef ecosystems rely on the base nutrients present in seabird guano to grow and generate new life. 

“When abundant, seabirds feeding in the open ocean transport large quantities of nutrients onto islands, enhancing the productivity of island fauna and flora,” explains Nicholas Graham, a researcher from Lancaster University.

This influx of nutrients from seabirds has been shown to increase fish biomass and improve the resiliency of corals in the face of warming oceans. In a recent study by Cassandra Benkwitt and Nicholas Graham of Lancaster University, after the mass bleaching event of 2015-2016 in the Chagos Archipelago, investigated the comparative recovery of islands with and without invasive rat species. The study determined:

Only seabird-rich island reefs experienced dramatic upswings in populations of crustose coralline algae, a type of hard-bodied algae that’s foundational to healthy reef systems.”

Furthermore, the native fish populations also recovered, whereas near invasive rat-infested islands, they are just a memory. 

It is imperative that as a global community, we further our efforts to restore native seabird populations and “more broadly, the maintenance of nutrient subsidies, via strategies including eradication of invasive predators, may be important in shaping the response of ecological communities to global climate change.”

Featured Image: Great Frigate Bird landing on an island in the French Frigate Shoals. Credit: Papahānaumokuākea Marine National Monument
Source: Anthropocene