VEGETATION RECOVERY AND HERBACEOUS PRODUCTION IN A FRESH-WATER WETLAND 19 YEARS AFTER A MAJOR OIL-SPILL

After a major oil spill in a fresh water wetland, the oil was set ablaze as a clean-up measure. Nineteen years later the vegetation structure of the wetland was analysed for evidence of and information about vegetation recovery. Our results indicate that vegetation in the area (zone 'H') which received the direct impact of the spill is recovering but vegetation in areas downstream of the spill site (zone 'M') is presently being degraded due to a slow seepage of persistent crude oil from the spill site. Herbaceous production (including food crops) was negatively correlated with hydrocarbon concentrations in the soil. The present results suggest that burning as a clean-up measure is ineffective, at least in wetland ecosystems.