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What Is Recovery?
We all have some idea of just what "recovery" is--we've all recovered from a cold or the flu--yet to ecologists studying natural systems, it is a very difficult term to define and measure. An ecosystem constantly adjusts itself to react to or compensate for changes in the environment, such as
- daily temperature variations;
- changing of the seasons;
- long-term drought;
- rare natural events, like hurricanes or earthquakes; or...
- ...oil spills.
When the Exxon Valdez spill occurred in 1989, the Prince William Sound ecosystem was responding to at least three notable events in its past:
- an unusually cold winter
- growing populations of reintroduced sea otters
- the 1964 Alaskan earthquake
Scientists studying the effects of the spill must evaluate their results against this background.
For our study, we do not define recovery to be a return to the precise conditions that preceded the oil spill. We know that is very unlikely to happen. However, we think that based on comparison to unoiled sites, there is a range of conditions that we can use to measure shoreline recovery from the spill.
For example, if we find that unoiled sites are changing in the same ways and at similar rates as the oiled sites, then we think the changes are probably caused by natural events and cannot be linked to the oil spill. If conditions at the oiled sites fall outside the range found at the control sites, then we suspect that oil contamination is still affecting these systems.
Just as humans differ in their ability to recover from injury, so do plants and animals. Some animals and plants are resilient and grow back quickly. In Prince William Sound, green algae and certain types of worms grew back the first summer. Rockweed and barnacles had repopulated many areas within two to three years. Other animals, such as clams, limpets, and some snails are taking much longer.
In short, we consider the intertidal communities we study to be recovering, but not recovered.
Other Pages in this Series
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