Aquacultural practices represent a considerable source of economic growth, supplying the livelihood of many stakeholders around the world. With the growing threat of climate change, aquacultural practices need to adapt to overcome the projected challenges.
Fish Farm. Image Credit: Andrey Armyagov/Shutterstock.com
Reviewing the effects of environmental change on capture fisheries and aquaculture
Fisheries and aquaculture are key for food supply, food security, and income generation. An estimated 43.5 million people work directly in this sector, with another 200 million livelihoods indirectly reliant as they occupy positions in marketing, processing, or distribution. Moreover, an estimated 20% of the average per capita of animal protein intake for more than 1.5 billion people is derived from aquatic foods.
However, since the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) in 2007, the threat of climate change to human society and natural ecosystems has been elevated to a top priority. The implications for sectors including fisheries and aquaculture are extensive, with increasingly worrying projections on the horizon.
Climate change effects will not occur in isolation but in conjunction alongside changes in land use, water flow, and physical-chemical consequences due to urbanization of coastlines. Additionally, the intensification of hydrological cycles is expected to affect limnological processes, increase runoff and discharge rates, as well as flooding extent. Such changes are predicted to increase in severity, frequency, and duration, affecting many aquacultural practices directly and indirectly.
Many effects from climate change on ecosystem and fish production have already been observed through the decline of global ocean primary production in recent decades. In addition, climate change is pushing many species ranges to toward the poles, expanding the range of warmer species but contracting those of colder-water species. This has been particularly noticeable among pelagic fishes, which have displayed changes in vertical movements as well.
Other impacts affecting aquacultural practices include changes in phenology. This includes changes in the timing of life-history events, which affects most strongly species with short lifespan including plankton, squid, and small pelagic fishes. This temporal shift also extends further as temperature-mediated stress will affect recruitment success among sedentary organisms, directly reducing the abundance of many aquatic species. Looking even further, impacts are predicted to affect net primary production and its transfer to higher trophic levels, as well as impacts on evolutionary timescales.
Such changes are expected to be exacerbated at the extremes of species’ ranges, as organisms will already occur among near-stressful conditions.
Nevertheless, uncertainties remain, in particular concerning the synergistic effects among stressors and the abilities of aquatic organisms of economic significance to adapt and overcome environmental changes.
Further implications of climate change for capture fisheries
Across reviews of scientific publications, a consensus has been reached on the predicted impacts of climate change as well as the necessary responses to these impacts. In particular, individual fishers and the communities they form may be most affected.
These include biophysical impacts on the distribution, or productivity of marine and freshwater fish stocks through processes such as ocean acidification, habitat damage, changes in oceanography, disruption to precipitation, and freshwater availability. Fisheries will also be exposed to a diverse range of indirect climate impacts, including displacement and migration of populations; impacts on coastal communities and infrastructure due to sea-level rise; and changes in the frequency, distribution, or intensity of tropical storms.
Recent reviews have also identified that the vulnerability of fisheries and fishing communities depends on their exposure and sensitivity to change as well as the ability of individuals or systems to anticipate and adapt.
This adaptive capacity relies on key assets and can be constrained by the culture or marginalization of communities. Moreover, the vulnerability of effects varies between countries and demographic groups within society, as poorer and less empowered countries are more susceptible to climate impacts. The vulnerability of fisheries is likely to be higher where they already suffer from overexploitation or overcapacity
In the longer term, adaptation to climate impacts includes reactive or anticipatory actions by individuals or institutions. Measures currently outlined include abandoning fisheries for alternative occupations, developing preemptive insurances and warning systems as well as changing fishing operations to accommodate for storm surges, fish displacement, and reduced stocks.
Fisheries governance in particular will play a key role as the range of adaptive options available will need to be account for rapid and unpredictable changes in stock distribution and abundance. Moreover, the overarching approach of governance towards equitable and sustainable fisheries is necessary, and accepting inherent uncertainty will also be a key principle. More literature is also focusing on ecosystem-based approaches, which may improve the adaptive capacity of fisheries.
However, adaptation may be costly and limited in scope, so that mitigation measures to minimize the impacts of climate change remain a key responsibility of governments.
Measures for aquaculture to counteract effects of climate change
Studies have also focused on addressing the impacts of climate change on the aquacultural sector as well as how to lessen the contribution of aquaculture to climate change, which encompasses the measures to counteract climate change.
Although resource-dependent communities have adapted to change throughout history, projected climate change comprises multiple, synergistic, additional risks to fishery communities that may limit the effectiveness of past adaptive strategies.
Around the globe, aquaculture is not practiced evenly. Most practices occur in Asian subtropical regions, with an estimated 65% of total aquaculture production is inland and concentrated there.
Moreover, the effects of climate change are also predicted to vary regionally, which means that the severity of economic impacts will be different across tropical, subtropical, and temperate regions, as well as among fresh, brackish, and marine environments.
Many uncertainties, therefore, remain when attempting to elucidate how impacts may vary across environments and regions, yet the consensus is clear, specific areas harboring the majority of aquacultural activities across developing countries will be most affected. These are therefore the focus of many policies. Recent studies have also emphasized the need for implementing policies across scales, both spatiotemporally, site-specific as well as on regional, national, and international levels.
The future of aquaculture, therefore, relies on the balance of effective policies related to active practices and the implementation of measures to mitigate and adapt to changes related to climatic change.
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