Abstract
Rates of biodiversity loss are higher in freshwater ecosystems than in most terrestrial or marine ecosystems, making freshwater conservation a priority. However, prioritization methods are impeded by insufficient knowledge on the distribution and conservation status of freshwater taxa, particularly invertebrates. We evaluated the extinction risk of the world's 590 freshwater crayfish species using the IUCN Categories and Criteria and found 32% of all species are threatened with extinction. The level of extinction risk differed between families, with proportionally more threatened species in the Parastacidae and Astacidae than in the Cambaridae. Four described species were Extinct and 21% were assessed as Data Deficient. There was geographical variation in the dominant threats affecting the main centres of crayfish diversity. The majority of threatened US and Mexican species face threats associated with urban development, pollution, damming and water management. Conversely, the majority of Australian threatened species are affected by climate change, harvesting, agriculture and invasive species. Only a small proportion of crayfish are found within the boundaries of protected areas, suggesting that alternative means of long-term protection will be required. Our study highlights many of the significant challenges yet to come for freshwater biodiversity unless conservation planning shifts from a reactive to proactive approach.
Highlights
Freshwater ecosystems occupy less than 1% of the earth’s surface, but support approximately 10% of the world’s species and 30% of all vertebrates [1]
Threat levels have been reported this way in Nearly one-third of the world’s crayfish species were assessed as threatened with extinction assuming that DD species are threatened in an equal proportion
There is an urgent need to better understand the extinction risk and patterns of threat in freshwater crayfish. We address these gaps by assessing the global extinction risk of all crayfish species described up to 2009, using the International Union for Conservation of Nature (IUCN) Red List of Threatened Species Categories and Criteria [32]
Summary
Freshwater ecosystems occupy less than 1% of the earth’s surface, but support approximately 10% of the world’s species and 30% of all vertebrates [1] These systems provide a range of valuable services, including fisheries, domestic and commercial water supply, carbon sequestration and energy; a rapidly growing human population has increased the demand on freshwater resources leading to a freshwater biodiversity crisis [2]. Species-specific data were collected on taxonomy, distribution, population trends, ecology, biology, threats and conservation measures for all 590 species of crayfish described up to 2009.
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