By Mark Yokoyama
In the last Bird Watch SXM column, we took a closer look at how drought conditions can impact migratory birds arriving to the island. Having had a few showers since then, perhaps it is time to look at how our wetlands get back to normal.
During our current drought, a lack of water has been the most obvious impact on our wetlands. Low water levels in the Great Salt Pond revealed the historic salt pans to a degree that hasn't been seen in recent years. Many ponds have dried up entirely. Wetlands are more than just water, though, and bouncing back from a drought takes time.
One of the more striking impacts of the drought has been the pink coloured water at Étang de la Barrière. This is caused by salt-loving microorganisms called haloarchaea, which require high concentrations of salt to thrive. The pink colour disappeared after just a few showers, illustrating how quickly the balance of microorganisms can change with salinity.
The refilling of ponds seems to have restarted, but is far from complete. The cemetery pond in Grand Case has a shallow layer of water, but most of Étang Chevrise is still completely dry. The rate at which each pond refills may depend on which areas receive rain and how much of that rain makes it to each pond.
Even a full pond can be a desert if it has no life. Snails, crustaceans, aquatic insects and fish are all key players in our wetland ecosystems. The rate at which they repopulate wetlands after a drought can depend on many factors. Many aquatic insects are able to fly, allowing them to colonize rejuvenated wetlands quickly. Other species, like fish, may need to wait until heavy rains fill channels between ponds that are otherwise isolated. The rate at which species reach a population equilibrium will depend on how quickly they mature and reproduce.
It may take years for some parts of our wetlands to recover. Mangrove trees in and around many ponds have died, perhaps in part due to the drought. Although these species can grow quickly, recovery will still take place over years, not months or weeks.
The recovery of our wetlands after a drought involves a collection of processes that takes place according to different timelines. In many ways, it is just an extreme version of what happens during the cycle of wet and dry seasons each year. This year, we may need to wait a little longer: the latest forecasts predict dry conditions this winter and into next spring. Only time will tell.