Healthy Ecosystems Depend on Smart Citizens
by Martha Blume
The northern snakehead fishs release to a pond in Crofton by a man tired of having it as a pet leaves me pondering how, 40 years after the term ecology was coined, many people still lack basic knowledge about the balances of nature. Ecologists call this balance of physical, chemical and biological components an ecosystem.
The prefix eco- means house, and system indicates a complex of coordinated units. Ecosystems around us include the Chesapeake Bay watershed, the ocean, a forest and, on a small scale, the pond in Crofton that snakeheads threaten to set off balance.
Ecosystems contain both living and nonliving components, through which nutrients are cycled and energy flows. The energy in an ecosystem is limited, which limits the number of organisms that can survive at each feeding level. The basic unit of the ecosystem is the population a group of animals of the same species living in the same area which occupies a particular niche, playing a particular role in energy flow and cycling of nutrients. A niche within a given ecosystem cannot be simultaneously and indefinitely occupied by more than one population.
New species are introduced to ecosystems in many ways. Often the introduction comes courtesy of an irresponsible pet owner, as in the case of the northern snakehead and the mute swan. Zebra mussels came our way in the ballast water of foreign ships. Exotic plant lovers gave us purple loosestrife. And people traveling with their belongings from one country to another brought us both the house mouse and phragmites. Such species are called invasive because they fit no preordained niche, may have no natural predators or control mechanisms and can take over more than their fair share of nutrients, crowding out natives and disrupting the natural cycles of the system. Garbage in, garbage out, as they say.
Animal rights activists plead that it is by no fault of the animal in question that it is here, and it has the right to live without threat of violence. (One hears decidedly less from animal rights activists in defense of the northern snakehead than one does for more cuddly or graceful creatures.) However, when a non-native puts an entire ecosystem in a poor state of health, all the species in it are at stake.
Do we sacrifice one individual, one population, for the sake of the health of the system? I think we must. I believe it must be done in as humane way as possible, with regard to the sanctity of all life, but I believe it must be done.
Better yet is to keep the invasives out in the first place. Interior Secretary Gale Norton was on the right track when she proposed banning the importation and sale of the northern snakehead in this country. She needs to go further.
Which raises the question of what other non-natives should be banned, both for the protection of ecosystems in this country and those worldwide. Most of what one finds in a pet store, other than domesticated mammals, would probably have been better off left in its native habitat. The market to satisfy Americans need for exotic pets, including tropical fish and jungle birds, exploits ecosystems around the world. As for non-native plants, a gardener needs to understand how they spread and how to contain them if they must be planted out of doors.
Pet owners should never release unwanted pets into the wild. This includes feral cats, which threaten native bird populations. Fishermen should dispose of live bait properly. Homeowners should plant more native plants. And we need to educate one another about the dangers of the release of non-natives to the environment.
The ecosystem is the sustaining unit. It must be kept healthy for those in it to survive. All of us are responsible for making it so.
Bay Weekly contributor Martha Blume holds a masters degree in environmental education from the University of Maine.