Conservation of the Matrix II: Salamanders in Headwater Streams
The second paper showing that what’s around an area can be critical to conserving what’s in it is by Winsor Lowe and Douglas Bolger of Dartmouth College.
Lowe and Bolger studied how logging near 25 headwater streams in New Hampshire affects spring salamanders, which are pink, up to 8 inches long, and rarely seen. Because amphibians are extremely sensitive to conditions in water as well as on land, they are good indicators of the overall ecological effects of logging. The researchers accounted for factors including the time since the last timber harvest, stream sedimentation, the presence of predatory brook trout, and the proximity of other salamander populations.
In the northeastern U.S., the diversity of stream amphibians is highest in headwater drainages. However, headwater streams are barely protected. For instance, they are often developed without mitigation under the Army Corps of Engineers’ current nationwide permits. Disturbance of headwater streams can increase flooding, erosion, and sedimentation downstream. Logging is the primary disturbance to headwater streams in the northeastern U.S.
Lowe and Bolger found that streams had more salamanders when they were confluent with another stream (that is, when two streams ran into each other) than when they were isolated. Notably, confluent logged streams had 40 percent more salamanders than isolated ones. This suggests that population connectivity may help protect salamanders in disturbed streams. The researchers speculate that confluent streams might benefit salamanders by letting individuals from an unlogged stream disperse to a logged one. “Dispersal might help prevent local population extinction in the disturbed streams,” they say.
The next step is finding out how the salamanders move from stream to stream. If they disperse via the riparian edge along streams, managers should extend protection of riparian areas along headwater streams (those further downstream are currently protected). On the other hand, if the salamanders disperse overland, then this needs to be accounted for when managers decide when and where to harvest timber.
Lowe, W.H. and D.T. Bolger. 2002. Local and landscape-scale predictors of salamander abundance in New Hampshire headwater streams. Conservation Biology 16:183-193.