7


Executive summary


Human pressures on the health of the oceans have continued to increase over the last decade, in concert with the growing human population and the expanded use of ocean resources (well established). Multiple stressors give rise to cumulative impacts that affect the health of marine ecosystems and diminish nature’s benefits to humans. However, there has been success in the management of some pressures, with concomitant improvements in ocean health, and these provide lessons on which to build. Out of numerous existing pressures we have selected three for particular attention in this Global Environment Outlook (GEO-6) assessment: bleaching of coral reefs; marine litter; and challenges to achieving sustainable fisheries in the world’s oceans. {7.1}


Tropical coral reefs have passed a tipping point whereby chronic bleaching has killed many reefs that are unlikely to recover even over century-long timescales (well established). Coral bleaching is due to warming of the oceans, which is in turn, attributed to anthropogenic emissions of green house gases (GHGs; especially CO2


) since the industrial revolution.


Ocean warming lags behind GHG emissions by several decades, such that the tipping point for coral reef bleaching was passed in the 1980s when atmospheric concentration of CO2


exceeded about 350 parts per million (ppm). {7.3.1}


Reef bleaching events now have a recurrence interval of about six years, while reef recovery rates are known to exceed ten years (established but incomplete). This means that, on average, reefs will not have sufficient time to recover between bleaching events and so a steady downward spiral in reef health is to be expected in coming decades. The oceans SDG target 14.2 “by 2020, sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience, and take action for their restoration in order to achieve healthy and productive oceans” may not be attainable for most tropical coral reef ecosystems. {7.3.1}.


There is evidence that reef death will be followed by loss in fisheries, tourism, livelihoods and habitats (inconclusive). The demise of tropical coral reef ecosystems will be a disaster for many dependent communities and industries, and governments should, over the next decade, prepare for the eventual collapse of reef-based industries. The contributions provided by coral reefs have collectively been valued at US$29 billion, which includes their value to tourism, fisheries and coastal protection. Losses to these sectors have not yet been documented but there is significant risk that losses will occur over the next decade. {7.4.1}.


Fisheries and aquaculture are estimated to be worth US$362 billion in 2016, with aquaculture contributing US$232 billion (established but incomplete). Mariculture is expanding but most of the increase is in aquaculture, especially inland aquaculture (established). Aquaculture provides more than 10 per cent of the total tonnage of fish production and this proportion is increasing. Together fisheries and aquaculture support between 58-120 million livelihoods, depending on how part-time employment and employment in secondary


processing is counted. The large majority of livelihoods are provided by small-scale fisheries and this has been stable for over a decade, yet commercial harvesting accounts for the large majority of commodity value, including more than US$80 billion per year exported from developing countries to international markets. {Table 7.1, 7.3.2}.


Fish, high in protein and micronutrients important for health, currently provide 3.1 billion people with over 20 per cent of their dietary protein, with higher proportions in many areas of the world where food insecurity is widespread (established but incomplete). To meet future challenges of food security and healthy populations, in addition to using all natural products harvested for food more efficiently, more fish, invertebrates and marine plants will have to be taken as food from the oceans and coasts, so both capture fisheries and aquaculture are expected to expand. {7.5.2}.


It is possible to keep capture fisheries sustainable, but this requires significant investments in monitoring, assessment and management and strong local community-based approaches (established but incomplete). Likewise, sustainable aquaculture requires knowledge and care in management of operations. {7.6}.


Reviews show wide variation among countries in the sustainability of their fisheries and aquaculture, with factors such as overall wealth to invest in fisheries research and management, while avoiding capacity-enhancing subsidies, strongly affecting the ability to keep large-scale fisheries sustainable (established but incomplete). For small-scale fisheries coherence of the social structures and cultural practices that promote effective community self-regulation strongly affect sustainability. {7.5.2}


The ecosystem approach to fisheries has been widely adopted in national and regional policies and operational guidance on actions to manage the footprint of fisheries has been provided by the Food and Agriculture Organization of the United Nations (FAO) (inconclusive). Despite the acknowledgement of the large footprint of fisheries on marine ecosystems and its full uptake in policy, measures to minimize the ecosystem effects of fishing have had mixed success. However, as with sustainability of exploitation of target species, in general the ecosystem footprint of by-catches, discards and negative habitat impacts of fishing gear is declining in the parts of world with sufficient economic resources to invest in fisheries monitoring and gear technologies that improve selectivity of harvest and reduce habitat impacts. This approach is also being applied in aquaculture, with comparable objectives and rapid uptake by the industry. {7.4.2}


The amount of marine litter continues to increase – an estimated 8 million tons (Mt) of plastics enters the ocean each year, as a result of the mismanagment of domesic waste in coastal areas (established but incomplete). Marine litter has been found at all ocean depths. Without intervention, the quantity of plastic in the ocean is expected to increase to 100-250 Mt by 2025. {7.3.3}.


176 State of the Global Environment


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