Drought Frequencies

Our results emphasize that several components of temporal variations in environmental conditions are critical to the persistence and abundance of snail kites. We found that simple modification of the amplitude of water level changes (while mean annual water levels were kept constant) could have dramatic effects on population growth. Surprisingly, it was not the scenarios with the largest amplitudes (largest differences between minima and maxima in water levels) that reduced the population...

Drought Duration

Another important hydrological variable related to temporal variability in water levels is drought or drydown duration (length of time an area is dry). We were able to vary drought duration in the model, and found significant effects on population growth rate. This response reflects the direct effect of drought duration on survival and reproduction. During droughts, snail availability is dramatically reduced (implicitly taken into account in the model), thus increasing the probability of kites...

Legacy Effects of Landscape Change

The ghosts of landscapes past have been found to haunt the biota of both terrestrial and aquatic systems. Land-use legacies on vegetation communities are especially prevalent and well documented. In central Massachusetts (USA), for example, the legacy of past agricultural land-use from the 18th century is still reflected in the vegetation of today's forests. This landscape has undergone a complete transformation during the past three centuries from a primarily forested region that was largely...