. The economics of biodiversity loss: Scoping the science . ? ? habitat area reserve area Figure 1. Hypothetical relationship between habitat area and fisheries production, represented in three ways, a) Relationship between area of a given habitat and fisheries production, for lower (blue) and higher (purple) thresholds, b) Relationship between fraction of a region reserved and fisheries production across the entire region, for low (blue) and high (purple) fishing effort, c) Relationship between the size an individual reserve and reserve effect (difference between fish biomass/density inside a
. The economics of biodiversity loss: Scoping the science . ? ? habitat area reserve area Figure 1. Hypothetical relationship between habitat area and fisheries production, represented in three ways, a) Relationship between area of a given habitat and fisheries production, for lower (blue) and higher (purple) thresholds, b) Relationship between fraction of a region reserved and fisheries production across the entire region, for low (blue) and high (purple) fishing effort, c) Relationship between the size an individual reserve and reserve effect (difference between fish biomass/density inside and outside the reserve, assumed to be an indicator of fisheries catches), assuming no relationship (blue) but an area threshold, or a positive relationship (purple). What are the main threats to the provision of marine fisheries? Human activities have now affected all oceans to various degrees (Halpern et al. 2008). Marine fisheries are under threat from different, but often interdependent and self- reinforcing, pressures (Pandolfi et al. 2005). Overfishing is the most widespread and the dominant direct impact on marine fisheries (Pauly et al. 2005). Fishing pressure is increasing as technological advances allow industrial fleets to fish with greater efficiency, farther offshore, and in deeper waters to meet the global demand for fish. Overfishing is in many parts of the world stimulated by subsidies which either reduce the costs of fishing or increase the net revenue fishers obtain (Pauly et al. 2005). Illegal, unregulated, and unreported (IUU) fishing is estimated to constitute a substantial fraction of the overall catches, undermining efforts for sustainable fisheries management (Pitcher et al. 2002). 88
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