The Falkland Islands (also known as Islas Malvinas) are a mountainous archipelago east of the southern border between Chile and Argentina. The islands are culturally and ecologically unique; while they are largely used for pasturing sheep, they also support a combination of species found on land in Patagonia (southern Chile) and in Antarctic waters. Now, a recent study indicates that seabird guano may be the reason why the Falkland Islands’ are covered in the iconic tussac grasses that these animals graze upon.
According to this study, the seabirds arrived to the islands approximately 5,000 years ago when the climate in the region was cooler and the birds’ preferred food was more abundant. After the birds settled on the islands, their nitrogen-ladden poop was deposited in the nutrient-depleted soils. This allowed the tussac grasses to prosper – even growing up to 1o feet tall in some cases – and increased wildfire incidents.
“Our study is unique because it documents a direct linkage across ocean and land ecosystems between top predators of the oceans –the seabirds– and island plant communities,” says Dr. Dulcinea Groff, the lead author of this study.
To determine the effect of the seabirds on the grasslands, a team from the University of Maine analyzed a 14,000-year-old peat records. Peat consists of damp sediments that are partially made up of decomposed vegetation. The researchers specifically analyzed undecomposed tussac samples preserved in the peat, which indicated that grass pollen climbed sharply within 200 years of the birds’ arrival. However, it is still unknown what caused the climate shift that motivated the birds to come to the Falkland Islands in the first place.
Today, these tussac grasslands are threatened by nearly 400 years of pasturing. And, as the South Atlantic Ocean rapidly warms, there is concern about whether the Falkland Islands will continue to be a suitable habitat for the seabirds — especially because it is unclear where they originated from when the climate abruptly cooled.
According to Groff, “our work emphasizes just how important the nutrients in seabird poop are for the ongoing efforts to restore and conserve their grassland habitats. It also raises the question about where seabirds will go as the climate continues to warm.”