Comment on Impacts of Biodiversity Loss on Ocean Ecosystem Services

In their recent paper Worm et al. (1) emphasize two important observations: that ocean biodiversity is generally beneficial for ecosystem services, including fisheries, and that numbers of overexploited or depleted stocks have increased over several decades. Both observations underpin the need for reducing fishing pressure and/or ensuring stock recoveries. Thus, the paper represents a useful contribution to the ongoing discussion. Unfortunately, the paper has two main flaws: Firstly the authors model the depletion of stocks as a function of time (year) which is then used to predict a 100% collapse for all taxa currently fished by 2048, whereas the maximum observed in their data was only 30%. Extrapolating 45 years into the future from a model with no mechanistic basis is extremely unsafe. Since the authors themselves mention "the inherent problem of inferring causality from correlation in the larger-scale studies" this prediction is even more problematic because it remains unclear how much any collapse can be explained by fisheries alone. Thus, it could be possible that the characteristics of the relationship will change at higher collapse levels (sigmoid, oscillating, ...). Secondly, the authors analyze the utility of marine closed areas and conclude that such closures, in general, are beneficial to marine ecosystems and fisheries. This analysis is based on a sample of case studies which is entirely unrepresentative of global fisheries; of the 49 papers which are the basis for this study, 27 are from coral reefs, while only 6 are from groundfish fisheries and none are from pelagic fisheries. The conclusions from such a subset cannot realistically be projected to the situation across global fisheries since groundfish and pelagic fisheries are by far the most important (2). 1) Worm et al. Science 314, 787 (2006). 2) The State of World Fisheries and Aquaculture (SOFIA) 2004 8221 FAO Fisheries Department, Rome, Italy (2004).

HOELKER Franz;  BEARE Douglas;  DOERNER Hendrik;  DI NATALE Antonio;  RÄTZ Hans-Joachim;  TEMMING Axel;  CASEY John; 

2007-06-04

AMER ASSOC ADVANCEMENT SCIENCE

JRC35570

https://publications.jrc.ec.europa.eu/repository/handle/JRC35570,   

10.1126/science.1139114,