Profound and pervasive degradation of Madagascar’s freshwater wetlands and links with biodiversity

RESEARCH ARTICLE Profound and pervasive degradation of Madagascar’s freshwater wetlands and links with biodiversity Andrew J. Bamford1*, Felix Razafindrajao2, Richard P. Young3,4, Geoff M. Hilton1 1 Wildfowl & Wetlands Trust, Slimbridge, Gloucestershire, United Kingdom, 2 Durrell Wildlife Conservation Trust, BP, Antananarivo 101, Madagascar, 3 Durrell Wildlife Conservation Trust, Les Augrès Manor, Trinity, Jersey, United Kingdom, 4 Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, United Kingdom a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Bamford AJ, Razafindrajao F, Young RP, Hilton GM (2017) Profound and pervasive degradation of Madagascar’s freshwater wetlands and links with biodiversity. PLoS ONE 12(8): e0182673. https://doi.org/10.1371/journal. pone.0182673 Editor: Maura (Gee) Geraldine Chapman, University of Sydney, AUSTRALIA Received: March 3, 2017 Accepted: July 21, 2017 Published: August 8, 2017 Copyright: © 2017 Bamford et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: Fieldwork was funded by the BBC Wildlife Fund (grant ref: BBCWF83, http://www.bbc.co.uk/ wild/). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. * Abstract Reflecting a global trend, freshwater wetlands in Madagascar have received little conservation or research attention. Madagascar is a global conservation priority due to its high level of species endemism but most work has focused on protecting forests. For the first time, we investigated the state of wetlands across the country to determine the effects of human disturbance. We conducted a rapid survey of 37 wetlands, using waterbirds and benthic invertebrates as ecological indicators. We recorded nine variables relating to human disturbance, revealing widespread wetland destruction. Principal Components Analysis reduced the nine variables to a single Principal Component (PC) that explained 50% of the dataset variance, demonstrating that different forms of human disturbance are ubiquitous and inseparable. The disturbance PC provides an index of how pristine a lake is and in Generalized Linear Models (GLMs) was significantly inversely related to the number of waterbird species present and the density of Chironomidae. The disturbance PC was estimated for every wetland in a GIS-derived dataset of wetland locations in Madagascar, giving a country-wide frequency distribution of disturbance. To validate the estimated PC values, we used the GLMs to predict the number of endemic bird species at an independent sample of 22 lakes. The predicted values correlated with the observed number of species, demonstrating that our procedure can identify lakes with high biodiversity value. The disturbance PC provides a convenient method for ranking sites, and a country-wide ranking demonstrates that the only near-pristine lakes in Madagascar are small sites that have been preserved by remoteness from human activity and not conservation management. The strategy of conserving high biodiversity remnants is insufficient because existing remnants suffer some degree of degradation and only support small populations of threatened species. Large-scale restoration of degraded wetlands is required for the long-term conservation of Madagascar’s freshwater biodiversity. Competing interests: The authors have declared that no competing interests exist. PLOS ONE | https://doi.org/10.1371/journal.pone.0182673 August 8, 2017 1 / 15 Degradation of Madagascan wetlands Introduction Freshwater ecosystems are the most threatened major habitat type globally [1], with freshwater vertebrate species declining faster than those in either terrestrial or marine realms [2]. Despite this, conservation research and investment in freshwater habitats is disproportionately low [3], with tropical wetlands particularly threatened and under-researched [4]. The main threats to wetlands globally are overexploitation of wetland resources including fish, pollution from agricultural and industrial processes, flow modification to provide water for cities and especially crops, habitat destruction or degradation, invasive species and climate change [5–7]. All of these problems are exacerbated by rising human populations, and tropical areas are seeing the highest rates of population growth and agricultural growth [7]. Tropical countries are also among the least well placed to deal with these issues due to generally very low institutional capacity [8]. Madagascar provides a good example. The country is of immense conservation interest for its high level of species endemism and threat, but activity has focused almost entirely on forests. Of the 46 Strict Reserves, National Parks and Special Reserves established before 2011, 45 protect forest ecosystems. As a result, Madagascar is losing wetlands faster than forest. Since 1960, the highland regions have lost 60% of wetlands, compared to 20% of forests [9]. Madagascar’s wetlands contain fewer iconic species than the forests, but show similar rates of species endemism [10,11] and are at least equally threatened. Half of the native freshwater fish species and half of the freshwater amphibians are classified as vulnerable or worse in the IUCN Red Data list [12]. Of Madagascar’s 12 bird species classified as Endangered or Critically Endangered, 9 are wetland birds. The only recent documented extinctions have been of freshwater species, the Alaotra grebe (Tachybaptus rufolavatus) and three fish species. Of the major threats to wetlands globally [5], not all are significant problems in Madgascar. Flow modification is a minor problem and the level of pollution is unknown in general, although it is high at some sites. Habitat degradation is a major concern, with two forms predominating–marsh clearance for rice farming and siltation caused by high rates of soil erosion from deforested land. Conversion to rice farming is the main cause of the loss of natural wetlands [9]. Invasive species include fish (tilapia, Oreochromis, Sarotherodon and Tilapia species, common carp, Cyprinus carpio, and Asian snakehead, Channa cf. striata) and plants (water hyacinth, Eichornia crassipes, and Salvinia molesta), although little is known about the effect they may have on aquatic ecosystems [13]. Madagascar is one of the poorest countries in the world and livelihoods are often wetland dependent. Half of the population, and 65% of the rural population, are dependent on unimproved water sources [14], such as rivers and lakes. Wetlands also supply most of the country’s staple foodstuff, rice, the majority of which is grow (...truncated)