Climate change impacts and vulnerability in Europe 2016

Climate change impacts on environmental systems
Figure 4.2
Projected change in global ocean surface pH
pH
8.1
8.0
7.9
7.8
7.7
7.6
2020 2040 2060 2080 2100
RCP2.6 RCP4.5 RCP6.0 RCP8.5
Note:
Source:
The figure shows the projected change in ocean acidity for various emissions scenarios (RCPs) until 2100. A decline in pH corresponds to
an increase in the acidity of ocean water. The thick lines show the model average and the shaded areas show the minimum to maximum
range for each RCP.
Adapted from IPCC (2013, Figure SPM7(c)).
Box 4.2
Ocean acidification effects on marine biodiversity
Ocean acidification can have a negative impact on the biology and ecology of numerous plants and animals (Secretariat of
the Convention on Biological Diversity, 2014). Impacts include the following:
• Phytoplankton form the base of many marine food webs. Any impacts on their survival and growth due to climate change
could therefore have major impacts on all other marine organisms and also affect commercial fisheries.
• Ocean acidification can affect a range of functions within organisms, such as membrane transport, photosynthesis in
plants, neural processes in animals, growth, reproductive success and survival. Effects can be seen at all levels ranging
from individual organisms to ecosystems. The effects on individual species depends on that species' capacity for adapting
to new conditions (Pörtner et al., 2014).
• The behaviour and sensory performance of marine fish could be impaired at the CO 2 levels projected in the ocean within
50–100 years (Welch et al., 2014).
• Acidification will affect species with calcium carbonate skeletons such as reef-building corals causing shifts from coral to
macroalgae dominance on reefs (Enochs et al., 2015).
• The effects of acidification can also include increased mortality and decreased fertilisation rates in sea urchins, decreased
calcification rates and reduced growth rates in mussels, oysters and abalones, and impaired oxygen transport in squids
(Fabry et al., 2008; Hall-Spencer et al., 2008). Many of these observations have been made in laboratory controlled
environments with a surface water pH that may be reached in 2100.
• Ocean acidification and synergistic impacts of other anthropogenic stressors provide the potential for widespread
changes to marine ecosystems (Fabry et al., 2008; Dupont et al., 2010).
• Acidification may not affect all marine environments uniformly. It may have the most effect in open oceanic waters, with
some coastal organisms appearing to be able to alter the pH of their calcifying environment as a result of temporal and
spatial variations in pH (Hendriks et al., 2014).
• Ocean acidification is happening, but the effects on marine biodiversity need to be better understood, especially in regard
to the synergistic effects of other stressors (Hendriks and Duarte, 2010; Hendriks et al., 2010).
110 Climate change, impacts and vulnerability in Europe 2016 | An indicator-based report