Critical Habitats and Biodiversity: Inventory, Thresholds and Governance

Marine habitats are extremely valuable in many ways (e.g., economically, culturally or for subsistence) and provide many necessary services for humans (Costanza et al. 1997, 2014). Despite their importance, coastal and oceanic habitats are increasingly threatened by fishing, climate change, oil and gas exploration, pollution and coastal development (Jackson et al. 2001; Halpern et al. 2008, 2019; Heery et al. 2017; Harris 2020). Habitat degradation and loss from these threats are not uniformly distributed and are cumulative with poorly understood interactions between pressures (Halpern et al. 2008). Despite the enormous impacts humans have had on marine ecosystems in the global ocean over the past 50 years, they tend to appear not as the complete extinction of individual species (Dulvy et al. 2003) but rather as changes in ecosystem composition and in the relative abundance and ecological status of individual species, along with more regional or local extirpations (Worm and Tittensor 2011). A species need not become globally extinct to radically alter the composition of the ecosystem (‘ecological extinction’), disappear from the local environment (‘local extinction’) or become commercially non-viable (‘commercial extinction’). Biodiversity loss is a globally significant symptom of unsustainable exploitation of Earth’s natural environment and a major threat to the ecosystem services on which we, and future generations, depend.