Wild Horses and Climate Change

Wild Horses and Climate Change

Assateague Island National Seashore, a 37-mile long barrier island off the coasts of Virginia and Maryland, is home to a band of “wild” horses. Technically considered “feral” (descendants of domesticated horses that have returned to a wild state), they are a huge reason people visit the island each year. The two million visitors in each of the last 10 years can not only experience these unique animals, but can spend time at the beach, surf, hike the island’s paths, or explore the island’s marshes. Assateague’s horses are tough. They face intense heat, hordes of mosquitos, poor food quality, and stormy weather. And with climate change affecting the island itself, their resiliency will increasingly be tested.

A mostly sandy island, Assateague’s shape and composition are sensitive to storms, wave action, and the rising sea caused by climate change. Barrier islands historically migrate towards land (from 3 to 5 feet per year), as sand from the eastern shore is deposited onto the island’s west side marsh in a process called “overwash.” But what has changed, according to research conducted at the Coastal Plant Ecology Lab at Virginia Commonwealth University, is that the “sediment movement from upland to marsh is being stymied by an expansion of woody vegetation brought about by a warming winter climate.” In other words, “the impact of sea-level rise on barrier islands in Virginia and elsewhere along the Atlantic Coast is being accelerated by climate change.” Colette St. Mary, a National Science Foundation Long-Term Ecological Research program director who worked with VCU on this study, says studying the connections between the island’s ecosystems is essential. “For example, coastal plant communities alter wind patterns and other variables, in turn shaping offshore islands. To address the effects of our changing environment, we need to understand this interconnectivity.” Satellite imagery shows that from 1984 to 2016, there have been gains and losses in backbarrier marsh and upland on the Virginia barrier islands. Over that 32-year period,  a net loss of 19% was experienced. The warming climate has led to an increase in woody vegetation of 41% which alters the rate of marsh to upland conversion.

The National Park Service (NPS) has developed a 25 to 30 year management plan for the island. After the devastation of Hurricane Sandy, NPS decided to accommodate the rising sea instead of trying to resist it. Parking lots and roads paved with asphalt are being replaced with surfaces that are more environmentally friendly so that, if washed away, they won’t harm the water. Also, ocean-side camping areas will most likely be moved in the next few years. And if conditions continue to worsen, driving on the island may no longer be permitted.

As for the Maryland herd, officials have determined the ideal size is between 80 and 100 horses. That range allows the island to maintain the health of the animals. To this end, the NPS began an adaptive management contraception program for the mares several years ago. Three new foals have been born into the heard this year, with a fourth expected yet this summer, bringing the current size to 77 (no mares received the contraceptive last year as the herd is just below the ideal range). The Assateague Island Alliance runs a “Foster a Horse” program in which people can become foster parents to members of the herd. The proceeds are used to help fund the Assateague Island National Seashore’s wild horse management program.

If you get a chance to visit this unique island, be sure to keep your safety and the safety of the horses in mind. It is important to remember these are wild animals. Feeding and petting them is strictly prohibited: the horses may become ill from eating human food and those that venture close to roads can be struck by vehicles. Visitors should maintain a distance of at least 50 feet from the horses at all times. According to NPS, “With careful management, the wild horses will continue to thrive on Assateague Island and provide enjoyment to thousands of nature enthusiasts, photographers, and people who just love horses!”

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