Exploring the benefits of a tropical, large-scale marine protected area for breeding seabirds, per mare, per terram

Abstract

Debate continues in scientific and popular literature into the benefits of large scale marine protected areas (> 100,000 km2 - LSMPAs), especially for top predators. Of top marine predators, seabirds are deemed to be the easiest to study due to their ease of observation and often colonial breeding. The Important Bird and Biodiversity Areas (IBAs) programme is a method of identifying the most important places for birds. IBAs are identified using a globally agreed standardised set of data-driven criteria and thresholds. In this thesis I explore the benefits of a LSMPA for top predators. I use IBAs on land and at sea with seabirds as the qualifying species as the means of exploration and the tropical British Indian Ocean Territory (Chagos) MPA (hereafter BIOT MPA) as the study system. Red-footed Booby Sula sula rubripes is the focal species of the thesis. My research demonstrates that the BIOT MPA is extremely important regionally and globally for biodiversity and provides a breeding sanctuary for ≈ 282,000 pairs of seabirds of 18 species annually, four of which breed in internationally important numbers that trigger IBA status. However, invasive Ship Rats Rattus rattus and abandoned coconut Cocos nucifera plantations are severely restricting the islands that seabirds can breed on. I calculate by eradicating rats and managing invasive coconut plantations on a single 123 ha island, the number of seabirds breeding in the BIOT MPA could more than double. At sea, I identified sites that meet IBA status and due to their overlapping boundaries form a single ‘super’ IBA that covers ≈ 10% of the MPA. The terrestrial and marine sites I have identified within the MPA warrant enhanced protection. Red-footed Booby is deemed an umbrella species and therefore protecting the feeding and breeding habitat of this species will afford protection on a suite of other species, including sub-surface predators. I suggest this thesis is a foundation stone from which further research into marine biodiversity hotspots in the central Indian Ocean can be launched. This thesis supports the growing evidence that tropical LSMPAs are beneficial to top predators and unequivocally demonstrates that the BIOT MPA encompasses the early stages of breeding of a highly mobile, top predator.