Interface ecosystems with an oil spill in a Venezuelan tropical savannah

Abstract

Frequent oil spills associated with oil operations in tropical savannas are developing new ecosystems that may be symbiotic interfaces between industry and environment. This paper describes these developments, the role of restoration efforts and uses ‘emergy’ to evaluate the changes. In April 1991, an estimated 36 000 barrels (5724 m 3) of 40 gravity crude oil were released into 4600 ha of tropical grassland-scrub and palm swamp communities from the blowout of a Venezuelan Oil Company well (Corpoven MUC-21) in Monagas State in eastern Venezuela. Ecologic and economic impacts of the oil spill were estimated using emergy analysis. The oil spill, its damages, and subsequent clean up were evaluated by comparing the emergy flows associated with each aspect of the spill and ecological restoration. Using emergy measures of solar emjoules (sej) and converting to macro-economic dollars (emdollars), total damages (including cleanup and spilled oil) amounted to 48.5 E18 sej or 11.3 E6 US emdollars. Environmental damages to ecosystems and agro-ecosystems amounted to about 22% of the total, while economic losses and costs of restoration were about 78% of the total. The area affected by spilled oil was divided into four zones based on post spill treatments and amount of spilled oil. The largest ecological impact was to a lightly oiled zone (about 4500 ha) but was relatively short lived having recovered ecological productivity (GPP) within 30 days. A zone where heavily oiled soil was removed (9 ha) and a third zone where heavy surface oil was burned (80 ha) made up a smaller fraction of total losses. The zone with soil removal was estimated to require about 15 yrs to recover, while the area that was burned was estimated to recover in about 10 yrs. A fourth zone that was heavily oiled but received no further treatments (11 ha) exhibited the smallest total losses and recovery was estimated to require only 5 yrs. A method is suggested for evaluating the benefit/cost ratio of ecological restoration projects using the four zones for comparative purposes.