Conservation
Wildlife, ecosystems and nutrient levels in Jordan Lake
On March 12, 2006, a joint meeting of the Bird Watchers of Carolina Meadows and the Orange/Chatham Sierra Club Jordan Lake focused on Jordan Lake. The evening began with a description of the chain of events spurred by the excess nutrients in the lake: the Environmental Protection Agency charged the state to reduce the amount of nitrogen and phosphorus flowing into the lake; the state assigned the Environmental Management Commission the task of writing new rules for those occupying the watershed that drains into the lake; the EMC, having met with many stakeholders, is writing new rules to guide behavior in the watershed. It will release a draft for public comment, revision, approval by the General Assembly, and finally, implementation. But like anything that mandates changes in behavior, the rules, even before their official release, have caused controversy. Stakeholders’ objections have delayed the process several times. The Sierra Club plans to participate in the public comment period when the rules are released.
This evening was part of an attempt to learn more about the lake to prepare for that part of the process.
The first of two speakers was Dr. Norman Budnitz of Duke University, who presented “The Birds of Jordan Lake.” His thirty years of experience with bird counts and surveys allows him to put the variations of individual species into historical perspective throughout the planning for the lake, the building of the dam, and the filling of the lake starting in September of 1981. The species that have benefited from the lake include ring-billed gulls, Canada geese, double-crested cormorants, great blue herons, osprey, and bald eagles. The charts of their populations all show a rise until 2003. Causes for declines since then aren’t clear. Other anomalies include the increase in the spring tufted titmouse population over the Carolina chickadees, which outnumbered them in the Christmas count. After Hurricane Fran, woodpeckers increased as the trees toppled by the storm died and became infested with insects, providing ample food for the woodpeckers. Then they declined again. But all these birds, along with turkey vultures, flourished on the scene of the new lake.
There are other birds whose populations have declined in the Jordan Lake basin. Some of the declines can be connected to the habitats that the lake changed. Cliff swallows still hang onto high branches over the water, but there are fewer barn swallows where the lake swallowed farmlands with their attendant barns, and fewer field sparrows and eastern meadowlarks where fields and meadows are under water. There are fewer house and purple finches as well as, for obvious reasons, fewer river-bottom warblers.
Other declines can’t be blamed on the lake: a drop in crow and blue jay populations after 2001, for instance, was probably caused by West Nile virus. Both groups are recovering. It is not clear why mourning doves have declined, or kestrels, but their populations have decreased elsewhere, too. The bobwhite quail has also declined locally and elsewhere, in fact, all over the east (possibly because of changes in farming practices affecting all open-field species), as have loggerhead shrikes, field sparrows, and eastern meadowlarks.
Then Catherine Deininger, Stream Steward Coordinator for the Haw River Assembly, talked about the problems excess nutrients create for the ecosystem, including the creatures in and around the lake. The easiest measure of the nutrients in the lake is chlorophyll-a, which indicates how much algae is present in the water. Although chlorophyll-a is necessary—it is the pigment that allows plants to use the energy of sunlight to make carbohydrates out of carbon dioxide—too much of it can cause problems:
When it dies, it sinks to the bottom, and, as it decomposes, it uses up too much of the oxygen dissolved in the water. All the creatures in the water can be affected, from the small amphibians, crustaceans, and insect larvae to the fish that eat them and the birds that eat both macro-invertebrates and fish. Eventually, the water could harbor toxic algae that are slimy and smelly, as well as poisonous—not good for a lake used not only for flood control (its original purpose) but also for drinking water and for recreation. Eventually, the lake could be hit by massive fish kills, as North Carolina has seen in some river estuaries near the coast. This possibility is especially dangerous during droughts, when less water means a higher concentration of nutrients. Droughts are likely if the climate in the area continues to warm.
Toxic algae haven’t appeared in Jordan Lake yet and the fish die-offs that occurred in the 1980s were small (under 1000 fish each). But the lake has seen pH levels that exceed state standards, and that also puts stress on aquatic life, for instance, making fish susceptible to disease. Many fish with sores have been seen in the lake as pH levels have risen.
Before we see the dire results of oxygen depletion, excess nutrients could favor some species over others. Dr. Budnitz said that the excess nutrients in the water cannot currently explain the variations he has seen in bird populations. Ms. Deininger said that in water with excess nutrients, some aquatic species might, in fact, thrive. The problem is that the diversity of species in the lake could drop and the whole system could be thrown off balance and crash. This is the catastrophic situation, with the lake unable to fulfill the many roles it has in our lives in the Piedmont, that we hope to avoid. This is what we hope the new rules—when they are finally released, discussed, approved, and implemented—will help to prevent. Look for information sometime in the fall about how you can participate in the public discussion about the Environmental Management’s Plan to protect the lake.
— Report by Judith Ferster
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