Abstract
Tortoises and freshwater turtles are among the most threatened taxa of vertebrates in the world due to consumption, urban development, agriculture, and land and water pollution. About 50% of the currently recognised chelonian species are considered threatened with extinction according to the IUCN Red List. Asia is an epicentre for the turtle and tortoise extinction crisis, containing the highest diversity of threatened species. In this study, we used species distribution models (SDMs) to assess the effectiveness of existing protected areas across Southeast and South Asia for the conservation of three large critically endangered freshwater turtles (Batagur borneoensis, B. affinis, and Pelochelys cantorii). We derived the models based on selected bioclimatic variables at the sites of known species records. Our SDMs showed that Indonesia is of particular importance in prioritising conservation for these three species, containing the largest areas of suitable habitat within protected areas. However, when considering water surface coverage, Thailand has the highest proportion of suitable areas under protection. Our results suggest that the present cover of protected network reserves seems inadequate in terms of size and should be expanded to sustain populations of the three target species. Therefore, we identified priority areas and reserves critical for further field surveys to guide the potential discovery of novel populations. To investigate the effect of climate change, we also projected potential distributions onto ensembles of four IPCC story lines. As a result, we found larger extralimital areas of suitable environment for all three species, particularly northwards and inland. However, high degrees of uncertainty in climate conditions indicate few reserves may provide long term protection. Lastly, we review the threats and propose recommendations for conservation of these poorly known freshwater turtles.
Highlights
Habitat loss due to land use changes is a significant factor leading to the decline of global biodiversity (Foley et al 2005)
We provided Maxent lambda files for more details on the assessment of the variables used in the models
Our results suggest that based on Protected Areas designated under the IUCN standards, Indonesia appears to be of major importance for conservation priorities in all three species for current and future scenarios
Summary
Habitat loss due to land use changes is a significant factor leading to the decline of global biodiversity (Foley et al 2005). South Asia and Southeast Asia have among the fastest rates of deforestation and habitat loss, with over 50% of native forest being depleted over the last two centuries (Sodhi et al 2004). This, combined with poaching, illegal pet trade, and land degradation, has resulted in habitat fragmentation as well as other negative impacts on the native biodiversity. The Asian continent is a hotbed for turtles facing extinction since it harbours 17 of the 25 (68%) most threatened chelonian species (Turtle Conservation Coalition [TCC] 2018, Rhodin et al 2018). Seven species and three subspecies (2.1% of all modern turtle taxa) have already gone extinct (TTWG 2017, TCC 2018)
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