Using marine biome maps to expand Marine Reserve network

Abstract

Compared to their marine counterparts, terrestrial biomes have long been known to the world (grasslands, coniferous forests, and tropical rainforests). Terrestrial biome mapping has been used frequently as a conservation tool. However, a global map of marine biomes (seagrass, kelp, zooxanthelate corals, and mangroves) is still lacking. Therefore this thesis aims to develop a complete global marine biome map with 30 arcsec (1 km x 1 km at the equator) resolution, and analyse its potential applications as a conservation tool. This study first modelled the global distribution of the seagrass biome and the kelp biome. The primary occurrence records and environmental variables were modelled using MaxEnt software, Version 3.3.1. The global extents of seagrass and kelp biomes were 1.6 x 106 km2 and 1.5 x 106 km2 respectively. These modelled biome layers and the existing mangrove and coral biome layers were overlaid to make a complete marine biome map using Arc GIS software. Because of marine biomes’ ecological and biological significance and increasing depletion due to anthropogonic activities, the conservation intiatives called for assessing the conservation status of biome species. Nearly 80% out of the 824 biome-forming species studied here had their conservation status assigned by the IUCN Red List, with the rest yet to be evaluated. Approximately 22% of species had been categorised as threatened, whereas almost none of the kelp species had yet been evaluated for their IUCN conservation status. Australia had the largest distribution of the seagrass, kelp and zooxanthellate coral biomes, while Indonesia had the largest mangrove distribution. A weighted sum analysis was carried out to identify the overlapping biome areas within a cell grid of 1 km x 1 km. Australia had the largest distribution of areas with a single biome and two biomes whereas Indonesia had the largest three-biome-inhabited area. The largest areas covered by multiple overlapping biomes were found in East and Southeast Asia, and Oceania regions. Only 1% of marine biomes were conserved in marine reserves globally. Delineating new reserves and expanding the exsisting reserves, especially in the countries and regions with multiple overlapping biomes will conserve marine habitat diversity, thereby conserving marine biodiversity.