Australia is a beautiful place to live. However, its southern parts were hit by severe droughts recently, resulting in serious financial loss for the farmers living in the region. Climate change is blamed for this bad situation to its farmers, their livestock’s, and crops. Humans as intelligent species may tackle this bad situation by adopting some remedial measures or taking subsidies from the government. But, what can other species do about it, particularly when they dependent on freshwater availability, need aquatic channels to migrate into suitable habitats for shelter, or are unable to move overland? Freshwater crayfish can be an excellent group of species to be considered for this investigation. First let’s know what freshwater crayfish are:
Freshwater Crayfish (also known as freshwater lobster, yabbies, crawfish, crawdads etc.) have been popular around the world for food consumption as well as pet business. They are distributed in more than 60 countries (they are completely absent from continental Africa and the Indian sub-continent), with 669 species currently identified globally. The major hotspots of crayfish species are found in the USA (~500 species) and Australia (~150 species). Crayfish have diverged about 115 million years ago (based on the fossil record), the period when Australia was attached to Antarctica and dinosaurs still roamed along the southern Australia river plains. However, our recent paper identified that a large proportion of global freshwater crayfish is vulnerable to climate-change impacts.
Freshwater crayfish are known to depend on four habitat types: streams, standing waters, burrows, and caves. The increased frequency and duration of droughts due to climate change may result in reduced flow regime and habitat connectivity and may affect the survival of crayfish that lives in burrows. Based on observations from cave-dwelling spiders, species that depend on caves may be as vulnerable to climate change, if not more, than species depending on other habitats.
Our recent article, from the research conducted for my MPhil degree has investigated the vulnerability of freshwater crayfish to climate change using the trait-based climate vulnerability assessment (TVA) protocol. But what is the TVA protocol? In TVA, several variables are collected, at global scale, to assess species’ three aspects that together define climate change vulnerability: inability to live in their habitats (sensitivity), inability to adapt to changing climatic conditions (low adaptive capacity), and high exposure to hostile environment (exposure). Variables are then scored as high or low based on some ecological conditions. For example, if a species is found to be dependent on a single habitat type (because under climate change if that habitat type is degraded/destroyed the species will be vulnerable) it will be considered as highly sensitive to climate change. If a species is known to live in areas surrounded by barriers that prevent it moving into favorable habitats to escape from climate change, it will be considered as low adaptive to climate change. Similarly, if species is known to occur in areas which are expected to see massive temperature or rainfall changes in the coming future it will be considered as highly exposed to climate change. For this assessment we had 17 such variables altogether. A species which is scored as highly sensitive, low adaptive and highly exposed to climate change is identified as vulnerable to climate change.
So, what are the outcomes from the assessment?
We found that 87 of 574 species of freshwater crayfish are vulnerable to climate change under a moderate climate change scenario (RCP6.0 for 2050). The study also showed that 87% of the species are highly sensitive to climate change (primarily due to habitat specialization), whereas 35% have low adaptive capacity and 57% are highly exposed. Hotspots of climate-change vulnerable crayfishes are concentrated in south-eastern USA (36 species), south-eastern Australia (21 species) and Mexico (10 species), reflecting global patterns of species richness. Of the 87 crayfish that are vulnerable to climate change, only 18 currently have climate change recognised as a threat on the IUCN Red List.
Hmmm … what are the observations from this assessment?
Comparisons with species listed as threatened on the IUCN Red List showed that many of our climate change-vulnerable species (41 species) are listed as threatened on the IUCN Red List. This implies that climate change vulnerability assessments generate additional conservation priorities to those identified by the IUCN Red List. These findings also coincides with studies that identified 22% reptiles and 11-15% amphibians and 6-9% corals species are vulnerable to climate change.
Only six species of crayfish (out of ~ 500 natives) are protected under the Endangered Species Act in the USA and 12 species (out of ~ 150 spp.) are protected in Australia under the Environment Protection and Biodiversity Conservation (EPBC) Act. As two major hotspots of climate-change vulnerability for crayfish are found in the USA and Australia, the study recommends that, further analyses should be conducted to assess in-situ protection levels of vulnerable species.
What should be next?
A global review for thermal tolerance of freshwater crayfish concluded that thermal tolerance data are available for only 6% of species and life history records are absent for the most of crayfish. We study conclude that, field data collection, thermal tolerance experiments and data collation efforts through regional and global assessments should be a key research focus for data-poor crayfish. Our study highlights that TVA protocol can help identify data gaps and key traits that should be investigated further and thus can help overcome knowledge shortfalls on the effects of climate change.
As an apex creature on earth, humans are responsible to save these beautiful creatures from climate change impacts.
Md Anwar Hossain 