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Impacts of climate change on global marine biodiversity and fisheries
- 1. Unpacking SROCC: Impacts and risks for global marine biodiversity and fisheries #SROCC COP25, Madrid 6 December 2019 Elvira Poloczanska WGII TSU
- 2. • The ocean warming trend documented in the IPCC Fifth Assessment Report (AR5) has continued • Since 1993 the rate of ocean warming has increased • Globally, marine heatwaves have doubled in frequency and become longer lasting, more intense and more extensive • The ocean has taken up 20-30% of total anthropogenic CO2 emissions since the 1980s causing surface ocean pH to decline • The ocean has lost oxygen over the upper 1000m Carbon emissions from human activities are causing ocean warming, acidification and oxygen loss
- 3. The ocean is projected to transition to unprecedented conditions Global mean sea surface temperature4 3 2 1 °C 5 0 –1 Marine heatwave days 20 15 10 5 Multiplication factor 1 Changes relative to 1986–2005 Historical (observed) Historical (modelled) Projected (RCP2.6) Projected (RCP8.5) 1950 2000 2050 2100 Ocean oxygen (100−600 m depth) 2 0 –2 –6 Percentage(%) –4 8.1 1950 2000 2050 2100 Surface pH 8.0 7.9 pH 7.8 Ocean heat content (0−2000 m depth)0.3 0.2 0.1 0 2400 1600 800 0 as sea level rise equivalent (left axis) as 1021 Joules (right axis) Metres
- 4. Response of species and ecosystems to climate change have been observed from every ocean region AR5 WGII
- 5. Many marine species across various groups have undergone shifts in geographical range consistent with warming Species in upper 200m Average shift rate: 52 km per decade Individual records of shifts Individual records of shifts
- 6. • Life is specialized on limited temperature ranges • In some marine ecosystems, species are impacted by both the effects of fishing and climate changes. • Altered interactions between species have caused cascading impacts on ecosystem structure and functioning. • Global warming and biogeochemical changes have already contributed to reduced fisheries catches in many regions Observed shifts in species composition, abundance and biomass production of ecosystems, from the equator to the poles.
- 7. Future ocean warming and changes in net primary production alter ecosystem biomass, production and community structure.
- 8. Future regional changes in animal biomass including fish and invertebrates Percent change Average by 2081–2100, relative to 1986–2005 Baseline Value in normalized index (1986–2005) >50 40 30 20 10 0 –10 –20 –30 –40 <–50 >3 1 0.5 0 No data Model disagreement RCP2.6 RCP8.5
- 9. Future regional changes in maximum fisheries catch potential (in shelf seas) Percent change Average by 2081–2100, relative to 1986–2005 Baseline Values in tonnes (1986–2005) >50 40 30 20 10 0 –10 –20 –30 –40 <–50 >275,000 55 0.15 0 No data Model disagreement RCP2.6 RCP8.5 RCP8.5 Global decrease 20.5-24.1% Tropical regions up to 50% decrease
- 10. Risks from future changes in marine species distribution and production to 2100 • The biomass of fish and catch potential decline on average, with regional increases • This has positive and negative impacts on catches, economic benefits, livelihoods, and local culture • Communities (eg Arctic, Small Island Developing States) that depend highly on seafood may face risks to nutritional health and food security • Challenges to fisheries governance are widespread under RCP8.5 with regional hotspots such as the Arctic and tropical Pacific Ocean
- 14. Strengthening response options • Reducing other pressures such as pollution and habitat modification • Policy frameworks for fisheries management, including strengthening responsiveness, and networks of protected areas • Strengthening precautionary approaches, such as rebuilding overexploited or depleted fisheries, and responsiveness of existing fisheries management strategies • Nature-based adaptation such as ecosystem restoration • Connections with local knowledge and indigenous knowledge • Such approaches bring multiple benefits for biodiversity, humans and, in some circumstances, climate mitigation
- 15. The more decisively and earlier we act, the more able we will be to address unavoidable changes, manage risks, improve our lives and achieve sustainability for ecosystems and people around the world – today and in the future.
- 16. More Information: Website: http://ipcc.ch IPCC Secretariat: ipcc-sec@wmo.int IPCC Press Office: ipcc-media@wmo.int @IPCC_CH @IPCC @IPCC www.vimeo.com/ipcc www.youtube.com/c/ipccgeneva Find us on:
Editor's Notes
- Over the 21st century, the ocean is projected to transition to unprecedented conditions with increased temperatures, greater upper ocean stratification, further acidification, oxygen decline, and altered net primary production.
- SROCC reinforces and adds evidence to the findings of AR5 that the impacts of climate change on species and ecosystems have been observed from every ocean
- Ocean warming has contributed to observed changes in biogeography of organisms ranging from phytoplankton to marine mammals (high confidence), consequently changing community composition (high confidence), and in some cases, altering interactions between organisms (medium confidence). Observed rate of range shifts since the 1950s and its very likely range are estimated to be 51.5 ± 33.3 km per decade and 29.0 ± 15.5 km per decade for organisms in the epipelagic and seafloor ecosystems, respectively. The direction of the majority of the shifts of epipelagic organisms are consistent with a response to warming (high confidence). The rate and direction of observed shifts in distributions are shaped by local temperature, oxygen, and ocean currents across depth, latitudinal and longitudinal gradients
- The rate and direction of observed range shifts are shaped by the interaction between climatic and non-climatic factors
- The global-scale biomass of marine animals across the foodweb is projected to decrease by 15.0 ± 5.9% (very likely range) by the end of the 21st century relative to 1986–2005 under RCP8.5 . These changes are projected to be very likely three to four times larger under RCP8.5 than RCP2.6
- Total animal biomass in the recent past (b, left panel) represents the projected total animal biomass by each spatial pixel relative to the global average. Future changes in animal biomass (including fishes and invertebrates) under low and high greenhouse gas emissions scenarios
- the maximum catch potential of fisheries projected to decrease by 20.5–24.1% by the end of the 21st century relative to 1986–2005 under RCP8.5 Future changes in maximum fisheries catch potential (in shelf seas) under low and high greenhouse gas emissions scenarios Changes in the ocean cause shifts in fish populations. This has reduced the global catch potential. In the future some regions will see further decreases but there will be increases in others.
- Projected geographical shifts and decreases of global marine animal biomass and fish catch potential are more pronounced under RCP8.5 relative to RCP2.6 elevating the risk for income and livelihoods of dependent human communities, particularly in areas that are economically vulnerable (medium confidence). The projected redistribution of resources and abundance increases the risk of conflicts among fisheries, authorities or communities (medium confidence). Projected geographical shifts and decreases of global marine animal biomass and fish catch potential are more pronounced under RCP8.5 relative to RCP2.6 elevating the risk for income and livelihoods of dependent human communities, particularly in areas that are economically vulnerable (medium confidence). The projected redistribution of resources and abundance increases the risk of conflicts among fisheries, authorities or communities (medium confidence). This includes potentially rapid and irreversible loss of culture and local knowledge and Indigenous knowledge, and negative impacts on traditional diets and food security, aesthetic aspects, and marine recreational activities
- Mobile species, such as fish, may respond to climate change by moving to more favorable regions, with populations shifting poleward or to deeper water, to find their preferred range of water temperatures or oxygen levels. As a result, projections of total future fishery yields under different climate change scenarios only show a moderate decrease of around 4% (~3.4 million tonnes) per degree Celsius warming. However, there are dramatic regional variations. With high levels of climate change, fisheries in tropical regions could lose up to half of their current catch levels by the end of this century. Polar catch levels may increase slightly, although the extent of such gains is uncertain, because fish populations that are currently depleted by overfishing and subject to other stressors may not be capable of migrating to polar regions, as assumed in models.
- Reducing pressure help species adapt Networks of protected areas help maintain ecosystem services, including carbon uptake and storage, and enable future ecosystem-based adaptation options by facilitating the poleward and altitudinal movements of species, populations, and ecosystems that occur in response to warming and sea level rise (medium confidence). Geographic barriers, ecosystem degradation, habitat fragmentation and barriers to regional cooperation limit the potential for such networks to support future species range shifts in marine, high mountain and polar land regions (high confidence). {2.3.3, 3.2.3, 3.3.2, 3.5.4, 5.5.2, Box 3.4} Strengthening precautionary approaches, such as rebuilding overexploited or depleted fisheries, and responsiveness of existing fisheries management strategies reduces negative climate change impacts on fisheries, with benefits for regional economies and livelihoods (medium confidence). Fisheries management that regularly assesses and updates measures over time, informed by assessments of future ecosystem trends, reduces risks for fisheries (medium confidence) but has limited ability to address ecosystem change. {3.2.4, 3.5.2, 5.4.2, 5.5.2, 5.5.3, Figure SPM.5} Terrestrial and marine habitat restoration, and ecosystem management tools such as assisted species relocation and coral gardening, can be locally effective in enhancing ecosystem-based adaptation (high confidence). Such actions are most successful when they are community-supported, are science-based whilst also using local knowledge and Indigenous knowledge, have long-term support that includes the reduction or removal of non-climatic stressors, and under the lowest levels of warming (high confidence). For example, coral reef restoration options may be ineffective if global warming exceeds 1.5ºC, because corals are already at high risk (very high confidence) at current levels of warming. {2.3.3, 4.4.2, 5.3.7, 5.5.1, 5.5.2, Box 5.5, Figure SPM.3} Restoration of vegetated coastal ecosystems, such as mangroves, tidal marshes and seagrass meadows (coastal ‘blue carbon’ ecosystems), could provide climate change mitigation through increased carbon uptake and storage of around 0.5% of current global emissions annually (medium confidence). Improved protection and management can reduce carbon emissions from these ecosystems. Together, these actions also have multiple other benefits, such as providing storm protection, improving water quality, and benefiting biodiversity and fisheries (high confidence). Improving the quantification of carbon storage and greenhouse gas fluxes of these coastal ecosystems will reduce current uncertainties around measurement, reporting and verification (high confidence). {Box 4.3, 5.4, 5.5.1, 5.5.2, Annex I: Glossary}
- The more decisively and earlier we act, the more able we will be to address unavoidable changes, manage risks, improve our lives and achieve sustainability for ecosystems and people around the world – today and in the future.