Climate change impacts on aquatic ecosystems are modulated by other forcing factors

EM 2 20 BarangeReducing overall stress boosts resilience to climate change

This article featured in EUROFISH Magazine 2 2020.

Currently Director of the FAO Fisheries and Aquaculture Policy and Resources Division and Honorary Professor at the University of Exeter (UK), Dr Manuel Barange is an ecologist and fisheries scientist interested in researching climate change impacts on marine ecosystems, their resources, and their implications for human society. Here he makes an eloquent case for management measures as the best way to limit the impacts of climate change and achieve sustainable fisheries.

Climate change is projected to have a negative impact on fish production particularly in tropical regions, where millions from often the most vulnerable layers in society are dependent on fisheries and aquaculture for their livelihoods and for nutrition. How can these groups be made more resilient in the face of these changes?

Climate change will change the productivity and distribution of many fish stocks. Our best projections suggest only a small global decline in potential catch by mid-century, but this masks important increases and decreases at regional level. Of particular concern is the projected decline in potential catches in tropical regions. FAO has developed an adaptation toolbox to guide countries in adapting their institutions, their management procedures, the livelihood opportunities of dependent communities, and on how to enhance their resilience to change. This toolbox is being implemented in a number of FAO field projects with the objective of enriching it with particular case studies, develop best practices, and scale it to larger regions, because regionally coordinated adaptation is important to share benefits and minimize impacts. It is clear that improved management can offset many negative effects of climate change, but the one adaptation we are not yet actively working on is consumer adaptation: distributional changes will affect what fish becomes available in fishmongers and supermarkets. We should eat what is available, not just what we are used to eat. Consumer adaptation is crucial to minimize the impacts of climate change and to transform food systems.

Biodiversity in European marine waters is under threat from a variety of anthropogenic factors, pollution, eutrophication, marine litter, hydromorphological pressures etc. Is climate change yet another source of pressure on biodiversity or could it also have a positive influence?

Climate change may be a simple problem to define and explain, but its consequences are complex, sometimes unexpected, and always diverse. The global reorganization of marine biodiversity is one such example. In general we expect tropical regions to experience a loss of species due to elevated heat stress, but we also expect the biodiversity of temperate and high latitude regions to increase as species migrate poleward. How to respond effectively to this ecological restructuring depends on how we define, now and in the future, our relationship with nature and thus with biodiversity.

Having said that, climate change is only one (even if increasingly dominant) forcing function. Other pressures, as listed in your question, may amplify or reduce the impacts of climate change. Reducing the overall pressures on marine ecosystems is the best recipe, and management is the best conservation tool.

The fact that climate change has an impact on fish stocks is fairly widely known even among the general public. That it also has implications for food safety is perhaps not quite as obvious. What are the main threats to food safety that stem from climate change and how can these be reduced?

Yes, you are correct. Climate change will lead to a series of more subtle impacts that are not yet well known by the public, and in fact are not yet fully understood by scientists. Pathogenic bacteria that occur naturally in waters (e.g. those that cause cholera or botulism), or are present in faecal waters (e.g. Salmonella), are known to grow faster in warmer waters and thus could pose additional risks in the future as they extend their distributional area. Excessive blooms of toxic algae are also a concern, such as of the dinoflagellate responsible for ciguatera fish poisoning. Although this disease was previously limited to tropical regions it now extending to temperate areas as waters warm. The toxicity and bioavailability of heavy metals is also affected by pH, which is decreasing as a result of climate change.

It is however important to keep these impacts in perspective. This is not a horror movie: the diseases and vectors we refer to are not new, but as their modus operandi may change we need to be ready for them. We need to reinforce our early warning systems, strengthen our risk assessment protocols, adapt our legislation, etc. In most cases we have the knowledge to act, but climate change is a moving target that requires adaptive and flexible solutions.

Freshwater aquaculture farmers in Central and Eastern Europe already experience some of the effects of climate change in the form of rising water temperatures, more unseasonal and more extreme weather events. What steps can they take to reduce their vulnerability to these phenomena?

Most of the impacts of climate change on particular aquaculture farming operations can be both favourable and unfavourable depending on the species considered, the farm set up, and its location. It is therefore difficult to generalize or simplify our messaging, but what we have been saying is that we have the tools to adapt. The problem is to identify what to adapt to in practical terms, how to adapt, and how to prioritize our actions. These are complex questions that have different answers if you operate at national level, at community level, or at the level of individual operators. From a national or supranational perspective the objective may be to identify how to reduce vulnerability. To do so farmers need to be supported to access and interpret the increasingly reliable projections of precipitation trends, temperature change, flooding/ draught risks, etc. This is crucial to understand how exposed they are to climate change. Second, they need support to increase their adaptive capacity: from diversifying the species farmed to integrating farming practices, from improving infrastructures to enhancing insurance protection. Many organizations are ready to support adaptation, and in fact many countries have listed aquaculture as an industry to reinforce as an adaptation measure to climate change. Again, the FAO Adaptation Toolbox has a full menu to guide managers and operators.

Many fish stocks in the Northeast Atlantic are subject both to the stress of climate change as well as of other conditions including pollution and habitat modification. The number of overfished stocks, though declining, is still significant. What are the implications for sustainable exploitation, in the face of so many different stressors?

This is a complex question, and in some ways circular. We know that where fisheries are intensively managed, like in the NE Atlantic in recent times, in the NE Pacific, in Australia and New Zealand, stocks are consistently above target levels or rebuilding. On the other hand, in places where fisheries management is not in place or is ineffective, the sustainability of fish stocks is deteriorating. The message is clear: the solution for fishery sustainability around the world is to implement effective fisheries management measures.

Other external factors, like pollution and habitat deterioration, can affect the productivity of fish stocks, but fisheries management would respond and adjust to these impacts, reduce overfishing and conserve the resource. I cannot repeat it enough: management is the best conservation, it is the only solution to the sustainability challenges we face.

In the Mediterranean and the Black Sea the majority of assessed stocks are overfished. The riparian countries are at different stages of development with disparate economic, social and environmental priorities. Climate change is an added complication. How can these various influences be reconciled to help both vulnerable fish stocks and vulnerable fishing communities?

According to the FAO SOFIA Report about 62% of Mediterranean and Black Sea stocks are overfished, while the assessment of the General Fisheries Commission of the Mediterranean (GFCM) is closer to 78%. The difference relates to how one defines a fish stock, but both of them are worrying. Indeed, the sustainability situation in this region is the worst of the areas FAO monitors. The reasons are complex, and related to the fact that riparian countries have very different socio-economic characteristics. In general, resource sustainability tends to fail most dramatically in places where poverty, hunger and conflict exist. Sustainability often stops being a priority! This is why the Sustainable Development Goals are interconnected and indivisible. If we do not end hunger and poverty our other objectives become unattainable.

Having said so, we must also acknowledge the progress made by the Mediterranean and Black Sea countries, supported by the GFCM. Up to nine multiannual management plans have been recently approved for stocks in the region, and eight new Fisheries Restricted Areas are in place, covering 22,500 km2. Almost 60% of the Mediterranean is already closed to fishing (1,700,000 km2) as part of a large deep-sea FRA. We are moving in the right direction, and political will is growing every year, but progress is still too slow.

Production from aquaculture has already overtaken that from capture fisheries and is projected only to increase in importance as a source of the global supply of fish and seafood. How significant is the threat of climate change for the aquaculture industry and are all forms of aquaculture, marine, freshwater, land-based, equally vulnerable?

The growth of aquaculture has been staggering, approximately 7.5% per year by volume since 1970. As almost 90% of the current global farmed food production is produced in Asia and over 60% in a single country, China, we see both opportunities and challenges. Opportunities because implementing Asia’s methods to other regions could significantly increase aquaculture’s contribution to food and nutrition security, but this is also a big challenge. The reasons why Africa (2.5% of production), Europe (3.7%) or America (4.2%) do not produce at the same level are complex: availability of land, access to finance and investment, costs and availability of feeds and fingerlings, insufficient biosecurity and disease controls, lack of legal frameworks, and underdeveloped value chains, are some of these reasons. As we approach 10 billion mouths we need aquaculture to almost double production by 2050. It can be done, but aquaculture growth rate has declined as production increased, and a concerted effort to tackle the issues I mention will be required.

The impacts of climate change on marine, freshwater or land-based aquaculture differ, of course. On land the challenge is availability of fresh water or aquatic ecosystems, which are affected by rain patterns, dams, irrigation, etc., while in the ocean the dominant forces are temperature change and acidification. Climate change changes everything, and whether a problem becomes a challenge or an opportunity depends on how one approaches it. We have the tools, but not necessarily the political will to be as innovative as we ought to be.

The fisheries and aquaculture sector is a source of some of the emissions that drive climate change. As is the case in other industrial sectors it too should reduce its contribution to global warming and other manifestations of climate change. What is the scope for improvement here and should it be led by the industry itself or is there a role for governments too?

Overall the fishing and aquaculture industries are estimated to release < 2% of the CO2 we emit to the atmosphere, so the gains would matter for the industry but may not necessarily make a very significant dent in our global emissions. Nevertheless, it is an obligation on all of us to reduce emissions and become carbon neutral. But to talk about greenhouse gas (GHG) emissions for a whole sector can be misleading, because there are good and not so good practices in the sector. Life Cycle Assessment (LCA) is a methodology for assessing environmental impacts associated with all the

stages of the life-cycle of a commercial product. Using this tool we know that the lowest GHG production per unit of protein is from mollusc and salmon aquaculture, as well as small pelagic, large pelagic and whitefish fisheries. Catfish and shrimp aquaculture production, and invertebrate and shrimp fisheries, are the largest emitters in the sector, with figures comparable to beef production.

What is evident is that there are significant opportunities for GHG reductions in both subsectors. In fisheries these include significant reductions through more efficient engines, propellers, hulls, fishing gears, lights, etc., as well as speed reductions. In aquaculture these include using renewable energies, integrating systems, and improving feed management, in addition to better species selection. These measures are easier to consider in some regions than others, because they require investments not available to many.

What policy recommendations with regard to climate change do you anticipate will be considered at the upcoming COFI meeting? In your opinion are countries treating the issue with the seriousness it deserves, initiating the measures necessary for the fisheries and aquaculture sector and the communities that depend on them to become more resilient? What role can FAO play in this regard?

Climate change has become the defining term in all our conversations, but turning this interest into practical action at sectoral level – other than the clear need to reduce emissions – has been less successful. This is not surprising: fisheries management relies on assessing what has happened in the recent past (assessing spawning stock biomass, recruitment, etc.) in order to determine what to do today (establish catch limits). Climate change demands that we look at what might happen in the far future instead, and adjust our present actions accordingly. We will also have to consider adjusting our principle of “managing for stability” to consider “managing for variability”. These are both significant paradigm shifts! In the marine fisheries sector the main issues lurking around the corner are the management and policy implications of stocks shifting distributions: do we have the institutions to cope with this (including multi-national arrangements), are our management processes flexible enough, will the industry be able to adapt and will dependent communities see the benefit? Perhaps most importantly, will the consumer accept change or reject it? You know, I lived in the UK for many years and used to buy two red mullet fillets for one pound. It is a fish from southern Europe and the fishmonger could not sell them! No fisherfolk can make a living if the customer is not prepared to pay for fish they have a lot of, but are not used to eat.

For aquaculture we see particular challenges in the competition for water with other sectors, particularly agriculture, and the infrastructure costs to cope with sea level rise and extreme events, among many others. But we also see opportunities in better genetic selection, alternative feeds, and low energy solutions. Eventually what we need is for climate change to be absorbed in all that we do rather than being talked about on the side, as a special problem. Everything we do in the future will include managing the impacts of climate change, it will be absorbed in all that we do, but this is another paradigm shift that will take time.