Mardi Gras in New Orleans means beads, booze, and boatloads of empty red crayfish shells, the byproducts of the world famous boiling competitions hosted on Bourbon Street each year. Yet across the pond in Europe’s waters, the stock of native crayfish are under fire, and the problem is growing as the temperature of our climate rises.
All five species of freshwater crayfish in Europe are currently facing diminishing habitats. To keep native crayfish on the plate, serious efforts need to be made to prevent invasive species from crawling into European waters as climate change is already affecting their habitats.
Three North American species of crayfish have already crawled into the lakes and watersheds of Europe, the products of careless dumping. These invasive species compete for the same resources the native crayfish need. Just like a pesky mother-in-law, the native crayfish spar with their distant evolutionary relatives, but the stakes in this competition are bigger than a family brawl- the crayfish are fighting for survival.
These North American visitors bring more than just hungry mouths and crawling bodies, they also bring A. astaci, coined the “crayfish plague,” a transmittable and deadly disease that has the potential to decimate the native European populations.
Crayfish face a triple threat. In addition to fighting off invaders and the constant fear of disease, global warming also threatens to alter natural crayfish habitats by moving their ideal habitats northward, out of range for these freshwater bound crustaceans, which cannot migrate on their own.
Researchers Cesar Capinha, Eric R. Larson, Elena Tricarico, Julian D. Olden and Francesca Girardi recently created a model to show just how much of their habitat these five species might lose in the coming years – and why we need to stop the losses.
Out in the field, the researchers hand-counted the number of each species of crayfish in small grids, thus calculating the population density of the animals, while they turned to historical records to see where each of the five native species originally ranged, and how these ranges have already diminished as American invaders lay claim to their habitats. Using this data, they created two future scenarios, using climactic variables from the past fifty years, one with low greenhouse gas emissions, and the other high. Extrapolation allowed them to project the climate in 2080, and the affect that greenhouse gas emissions could have on crayfish habitats.
The results are disturbing. According to the model, every single species of native European crayfish will see a reduction in habitat based on climactic factors by 2080. Under high greenhouse gas emissions, noble crayfish could see their habitats reduced up to 71% over the next 67 years. Even the white-clawed crayfish, facing the smallest reduction in habitat, could see a 19% reduction in the area it is able to survive in.
About 70% of planet Earth is covered in ocean. Imagine stripping away the Earth of every single drop of ocean water, leaving only land masses, that is the same percentage of habitat that the noble crayfish could see destroyed in the coming decades.
Another unsettling prediction of the model involves invasive species. Native crayfish can withstand temperatures of about 75 degrees Fahrenheit. As temperatures rise, their potential habitats decrease, as they can generally endure temperatures up to 86 degrees Fahrenheit. One invasive species, the red swamp crayfish, may even benefit from increasing temperatures, with a potential growth in range of 50%, creating an even greater overlap of native and invasive species, and greatly increasing the risk of the spread of crayfish plague. The noble crayfish, seen above to have the greatest potential decrease in habitat, might even share a complete range with invasive species by 2080.
In short, climate change brings dangerous changes to the habitats of crayfish, which, coupled with the intense threat of invasive species, may require human interaction in the near future.
Before they are boiled away, crayfish need to be supplanted to watersheds beyond their original ranges, or isolated in environments where invasive species can be monitored and destroyed, reducing the chance of crayfish plague spreading to native species, and increasing the chances of a diverse array of crayfish species flourishing in Europe.
Capinha, C., Larson, E. R., Tricarico, E., Olden, J. D. and Gherardi, F. (2013), Effects of Climate Change, Invasive Species, and Disease on the Distribution of Native European Crayfishes. Conservation Biology, 27: 731–740.
– Kira Clingen (modern)