The global context

The International Union for Conservation of Nature (IUCN) has identified climate change as the fastest growing global threat to all protected areas, including MPAs. Impacts affecting marine and coastal ecosystems are discussed in detail by the Intergovernmental Panel on Climate Change (IPCC) in its Special Report on the Oceans and Cryosphere in a Changing Climate (SROCC) (IPCC, 2019).

Some widely accepted indications of the impacts of climate change include:

• An increase in global mean sea levels of around 25cm since 1880, with the rise continuing at an accelerating rate, up to metres of rise over coming centuries (CSIRO & BOM, 2020).

• A rapid increase in the global ocean heat content since the 1950s.

• A dramatic decrease of sea ice extent in the northern hemisphere (Lindsey & Scott, 2020).

• An increase in the frequency, persistence and intensity of warm episodes of the El Nino-Southern Oscillation (ENSO) events since the mid-1970s, compared with the previous 100 years.

MPAs currently comprise around 7.7 per cent of the world’s oceans (MCI, 2021). Even if proposals to protect 30 per cent of the ocean by 2030 are realized, and assuming all those MPAs are well managed and “climate-ready”, the remaining 70 per cent will still be subject to a wide range of pressures including climate change. Given the fluid nature of our oceans, concurrent actions for waters outside MPAs are also necessary if MPAs are to be sustained over the longer term.

Experts believe there is still time to avoid the most negative outcomes by reducing greenhouse gas (GHG) emissions (Simard et al., 2016). But this requires far greater political commitment than is currently being shown (see in the chapter “What limitations and gaps can we find? “). It will also require investment in new technologies and infrastructure, though this is predicted to bring long-term financial benefits (see Section 3.2.1).

Regional differences

Climate impacts vary in different parts of the ocean. Many publications document current and projected impacts for specific regions, including:

• UK - Marine Climate Change Impacts Partnership – 2020 Report Card

• Australia - State of the Climate (CSIRO & BOM, 2020) – 2020 Report

• Europe - National climate change vulnerability and risk assessments - 2018 Report

• USA - Climate Change Impacts - 2014 National Climate Assessment

• Pacific - Climate Change in the Pacific: Scientific Assessment & New Research - Regional Overview and Country Reports.

For example, projections for Australia include (Hobday & Lough, 2011), with very high confidence, that hot days will become more frequent and hotter, sea levels will rise, and oceans will become more acidic. With lower confidence, they say that extreme precipitation will be more intense and tropical cyclones will be less frequent but more intense.

Not all climate stressors will impact every marine species or habitat the same way. Some species can acclimatize, and some populations may adapt. While many marine organisms are already being adversely impacted by climate change (e.g., corals, see Coral reefs and climate change below), some are expected to benefit (e.g., some sharks and jellyfish are predicted to have increased distributions).

Synergistic impacts

Synergistic or combined impacts of multiple climate stressors are expected to be greater than the impacts of individual stressors for our MPAs (Zscheischler et al., 2018). Traditional risk assessment methods typically only consider one hazard at a time, potentially leading to an underestimation of the risk, as the processes that cause extreme events often interact. For example, warming decreases oxygen concentration while increasing the metabolism and oxygen demand of most fishes and invertebrates.

Coral reefs and climate change

Nature-based management approaches 

Long-established, well-functioning and healthy MPAs are inherently more resilient to climate change impacts and can help halt biodiversity loss and soak up carbon emissions (Laffoley & Grimsditch, 2009). Management options are focusing increasingly on nature-based solutions such as conserving, restoring or better managing ecosystems to minimize climate change impacts.

For example, efforts are underway around the world to protect, enhance and restore mangrove swamps, salt marshes, seagrass meadows and kelp forests. In the UK, Project Seagrass is laying rope and seed to create new seagrass meadows and kelp is being reintroduced; the Wallasea Island Wild Coast Initiative is building up salt marshes using material dug out for the Crossrail tunnel in London. In Kenya, where mangrove wood is used for charcoal, shipbuilding and carpentry, conservation organizations are working on long-term mangrove restoration projects.

Nature-based solutions may require changes in management approaches and policy arrangements for adjoining areas outside MPAs, especially if the current situation limits adaptation responses within your MPA. For example, increasing precipitation may result in greater sedimentation within the catchments adjoining a coastal MPA, which in turn will affect coastal planning.

Hoegh-Guldberg et al. (2019) suggest the ocean itself should be considered as a solution to climate change, proposing five areas of ocean-based climate action:

• Ocean-based renewable energy

• Ocean-based transport

• Coastal and marine ecosystems (e.g., blue carbon)

• Ocean-based food (including aquaculture and shifting human diets towards seafood)

• Carbon storage in the seabed (although limited due to unknown risks).

Blue carbon is rapidly gaining interest (Laffoley & Grimsditch, 2009), and guidance for MPA managers in the assessment, protection and management of blue carbon habitats and processes is important (e.g., Hutto et al., 2021). Marine World Heritage properties contain around 15 per cent of global blue carbon assets despite covering less than 0.57 per cent of the ocean (UNESCO, 2021).

There remains some debate regarding the blue carbon concept, with critics maintaining the potential mitigation effects on climate are limited. Climate change itself poses a threat to blue carbon ecosystems: for example, marine heatwaves and intense storms can lead to seagrass die-off and the release of the carbon stored in its root systems. However, compared to the geoengineering proposals, nature-based solutions have been demonstrated to work and are far less risky (see in the chapter “Which sciences, technologies and innovations are emerging? “). Nature-based solutions will have other positive impacts and every action helps, but the actual climate mitigation gains should not be oversold.