Maryland’s Elusive Salamander Species

5 ‘Indicator Species’ That Reveal Environmental Health

Back in the day, coalminers relied on canaries to clue them in on potential danger. With their small lung capacity and unidirectional lung ventilation system, these feathered friends were more sensitive to carbon monoxide and methane gas than their human companions. Coalminers would know to evacuate when the birds became sick.

Present-day scientists use “indicator species” for a similar purpose: These organisms—whether plants or animals—provide clues about the environment around them. Here are a few examples:

Brook Trout

Brook Trout

The Northeast brook trout require nothing but the best possible water conditions to thrive. It’s because of their high standards that they’re considered an indicator species. When something’s not quite right in a watershed, brook trout are the first to go. Any drop in their population serves as a red flag for poor water quality or negative effects of human activities, such as dam operations, logging and pollution.



U.S. Fish and Wildlife Service

Ospreys are a valuable indicator species for a few reasons: 1) They’re at the top of the food chain, which means they’re likely to be affected by any environmental changes. 2) They’re highly visible, making them easier to monitor. 3) They have one main food source—fish—and they hunt only in a very specific area (i.e., close to the nest). If something’s affecting the fish population, the ospreys will have some telltale signs indicating a problem.

Bay Grasses

Bay Grasses

Animals aren’t the only ones that expose the problems happening in our waterways. Plants, such as Bay grasses, are monitored annually by such organizations as the U.S. Fish and Wildlife Service and the Virginia Institute of Marine Science. These experts can find clues about water quality in the prevalence of this species. It thrives in clean water and is sensitive to pollution.

During years of drought, these grasses have shown dramatic increases since the lack of rain essentially puts a stop on polluted stormwater that typically enters the Bay from the surrounding watershed. The reverse also happens: During an excessively wet year, stormwater runoff can flood the Bay with excess nutrients and sediments, causing a substantial decrease in this underwater vegetation. Whether its population is up or down, it’s a direct indication of the Bay’s health.

River Otters

Because of their sensitivity to pollution—and the fact that they’re at the top of the food chain—North American river otters are an excellent indicator species for habitat and water quality. If the water quality decreases, the otters’ prey could be affected, leaving these cute carnivores out of a lunch. The otters would leave the area, and their disappearance would signal an unbalanced or unhealthy ecosystem to the experts monitoring them.

Hellbender Salamanders

Hellbender Salamander

Image courtesy of the U.S. Fish and Wildlife Service Southeast Region

Maryland’s most impressive salamander is also the most valuable for biologists monitoring the health of our watershed. These 2-foot-long amphibians prefer clear, fast-flowing streams and rivers, and are particularly sensitive to pollution, habitat alteration and other environmental changes. Human activities like damming, channeling and dumping silt into waterways can slow the flow of water and cause a drop in nearby hellbender populations. Pollution from coal mining and agriculture also takes a toll on this species. A shift in hellbender prevalence gives experts the hint they need to start searching for an environmental problem and remedying it.


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