UC San Diego
Linking coral reef health and human welfare
- Author(s): Walsh, Sheila Marie
- et al.
Globally, 7̃00 million people depend on coral reef goods and services. However, over half of coral reefs are threatened due to global warming, fishing, and nutrient pollution. Using ecological and economic methods, I evaluated 1) the ecosystem-scale effects of fishing and nutrients, 2) the effects of fishing on condition and reproduction in a reef fish community, and 3) an integrated conservation and development program (ICDP). The Republic of Kiribati, Central Pacific, provided two natural experiments for this research. A population re- settlement program and island-wake upwelling on Kiritimati Island created orthogonal gradients in fishing and nutrient inputs. Fishing sequentially down trophic levels and size-classes had an in-direct effect on the reef community because of the loss of herbivores. Herbivorous fish controlled algal overgrowth of corals in the presence of nutrients and herbivory was enhanced under high nutrient conditions due to a shift in the algal community composition. Fishing also had individual level effects on the fish community. Under low fishing conditions (high predation conditions), prey fish species from five trophic groups (predator, benthic invertivores, planktivores, omnivores, and herbivores) had poor condition. Poor was only associated with higher reproductive effort when food resources were limiting. These results suggest that managing fishing should be prioritized. The Government of Kiribati subsidized copra, coconut agriculture, in order to reduce fishing and improving welfare. Households had perverse and varying responses to the policy. Households that enjoyed fishing increased fishing effort. Households with little benefit from additional cash goods reduced copra effort. In aggregate, fishing labor increased 33%. Although welfare improved or was unchanged for the majority of households, future welfare losses are expected due to declines in coral reef health. Four conclusions emerge from this research. First, there is no evidence for trophic cascades; fishing top predators will not benefit corals. Second, preferred fishing grounds, in upwelling zones or near pollution sources, may be more vulnerable to the effects of overfishing. Restoring top predators may have positive consequences for fisheries productivity by increasing prey fish reproductive effort. Lastly, fishing is not just a job. ICDPs that subsidize alternative incomes may actually be subsidizing overfishing