Invasive Assateague Horses?

The horses of Assateague are in the news (Wash. Post 16 Dec 06). Too many horses that must eat whatever grows on the island are laying waste to the vegetation. Piping plover (Charadrius melodus) and sea-beach amaranth (Amaranthus pumilus), native to the barrier islands, are among the many animals and plants that are threatened by mass over consumption by the horses. They are part of a complex system which ultimately provides the food source for the “wild” horses. The horses, of course, are the reason there is interest among the general public, who most likely are unaware of the native plants. The horses are part of American culture, and are not part of the pre-colonial ecosystem. They are, dare I write this, an invasive species.

No one within the National Park Service is suggesting removing the horses, but they are attempting to control the population pressure. The control of population is a cost to society, which because of the iconic nature of the horses, we shall find a way to bear. The Park Service will have to either weed out some horses or initiate an integrated pest management strategy balancing the need to continue the tradition while maintaining the ecosystem. If the horse population is allowed to grow unchecked, the island will soon be unable to supply the food needs of the animals, and we will be left with a herd of “wild” horse which we would have to feed and water, living on a barren desert isle.

If the horses were not present on the island, the land managers would be fighting a host of other potential exotic invaders, which would have a smaller feature on the science page of the newspaper. The exotic non native is the reason for the destruction on the island and the reason for the information to appear on the front page, rather than buried, if lucky, in the back hinterlands of the local paper.

But there is one further twist that presents itself: Deer, specifically, eastern white-tailed deer. We in suburbia, who attempt to garden understand the feeding habits of deer. First plants to go are five hundred dollar hostas, followed by almost all natives, followed pretty much by everything else. After they have eliminated all edible flora except for truly hardy and prolific invasives such as English ivy, the family car’s bumper is on the dinner schedule. Deer lovers, of course, react to gun-toting gardeners with suspicion and outrage, without considering the effect on the woodlands if gardeners stopped continuously refurbishing and replenishing the beloved deer herds’ supplemental food supply.

The deer, which are native, and the horses, which are not, together outline starkly the problem; too many or too much of something, out of control and out of balance, may result in the destruction of all, as we know it at the time. The process of life will compensate, as will be seen, if the deer are not checked, or the horses managed, for at some point, we will be unable or unwilling to pay the price or the piper to feed the animals and the herd will starve until such time as it is either reduced in number or eliminated.

It must be noted that by casual acquaintance to the federal definition, deer are not invasive, but rather a nuisance and I suppose that the horses at this point are technically invasive, but that is another essay.