The US Geological Survey (USGS) in its most recent report has indicated climate change as the culprit behind the drastic reduction in horse shoe crab population. In fact, the report references the measured rate of their decline in numbers to figures associated with the end of the last Ice Age the report specifically stated. The USGS based its findings with Genomics, the scientific discipline by which it’s able to assess historical trends in population sizes. Furthermore, scientists through the same field of study predict that numbers in horse shoe crabs may continue to decline because of predicted climate change, the USGS said.

Despite horse shoe crabs being heavily harvested for fishing bait or the pharmaceutical industry, scientists at the USGS are able to calculate exactly how much climate change has appeared to have historically played a part in their diminishing population by gauging sea levels. The USGS has inferred that oceans have been altered by climate change and will continue to jeopardize the successful reproduction of horse shoe crabs which need a precise temperature and depth of water with beach in order to mate. Even the US National Oceanic and Air Administration in its latest report confirm findings that climate change is in fact altering sea levels.

“Predicted future climate change, with its accompanying sea-level rise and water temperature fluctuations, may well limit horseshoe crab distribution and interbreeding, resulting in distributional changes and localized and regional population declines, such as what happened after the last Ice Age,” the report stated. “Using genetic variation, we determined the trends between past and present population sizes of horseshoe crabs and found that a clear decline in the number of horseshoe crabs has occurred that parallels climate change associated with the end of the last Ice Age,” said Tim King, USGS scientist.

Such claims are definitely corroborated having extrapolated data from Florida to Maine as well as a majority of the Gulf of Mexico. As seen there, the drastic reduction in population will have long term and reciprocal effects, King asserts. For instance, Atlantic loggerhead sea turtles, which used to feed mainly on adult horseshoe crabs and blue crabs in Chesapeake Bay, already have been forced to find other less suitable sources of food, perhaps contributing to declines in Virginia’s sea turtle abundance. Horse shoe crab eggs are an important source of food for millions of migrating shore birds as well.  Population decline has been registered officially since the 1990s between shore birds and horse shoe crabs respectively. However, horse shoe crabs have experienced the most dramatic changes in population since.

“Consequently, harvest limitations on females in populations with low numbers may be a useful management strategy, as well as relocating females from adjacent bays to help restore certain populations,” King said. “Both studies highlight the importance of considering both climatic change and other human-caused factors such as overharvest in understanding the population dynamics of this and other species.”