Living Blue Planet Report

Chapter 2: Our ocean under pressure page 33

Climate change

The ocean regulates our climate and drives the weather determining

rainfall, droughts and floods. Ocean waters also absorb vast

amounts of CO 2 , helping to mitigate human-caused global warming

and climate change. Indeed, in the last 200 years, the ocean has

absorbed around a third of the CO 2 produced by human activities

and has absorbed over 90 per cent of the extra heat trapped by the

rising concentrations of atmospheric greenhouse gases (Gattuso et

al., 2015).

Impacts on key marine and coastal organisms, ecosystems,

and services are already detectable, and several will face a high risk

of impacts well before 2100, even under the low-emissions scenario

(Gattuso et al. , 2015). By absorbing CO 2 , the ocean is becoming

more acidic – now occurring at a rate that is faster than any other

period in the past 65 million years. Warming and acidifying oceans

amplify the impact of other pressures from overfishing, habitat

destruction and pollution. For example, the increased acidity of the

ocean reduces the ability of coral reefs to re-establish themselves

(“bounce back”) from disturbances such as bleaching, cyclones and

crown-of-thorns starfish outbreaks (Hoegh-Guldberg et al., 2015).

If current rates of temperature rise continue, the ocean will become

too warm for coral reefs by 2050 (Hoegh-Guldberg et al., 2007).

This would mean a major disruption to at least 25 per cent of the

biodiversity in the ocean, as well as the loss of productive fisheries

and significant impacts on industries such as tourism. The loss of

reefs as a barrier would increase the exposure of coastal areas to

waves and storm systems.

Coastal systems and low-lying areas are also increasingly

experiencing adverse impacts from sea level rise – submergence,

coastal flooding, and coastal erosion. The loss of coastal ecosystems

such as mangroves and seagrass beds increases vulnerability of

coastlines and people to the impacts of climate change. Many low-

lying developing countries and small island states are expected to

face severe impacts that, in many cases, could result in displacement

of people, damage to ecosystems, and adaptation costs amounting to

several percentage points of GDP (IPCC, 2014).

Rising sea levels

 threats to low-lying

coastal areas

Climate change

and the ocean:

Key risks

Extreme weather

events and reduced

ecological resilience

 coastal inundation

and habitat loss

Shift in distribution

of fish and

invertebrates due to

warming waters 

decreased catches in

tropical regions

Loss of coral reefs
due to warming
and acidification 
reduced biodiversity,
fisheries production
and coastal protection

Loss of livelihoods,

coastal settlements,

infrastructure, ecosystem

services and economic

stability