Climate change impacts and vulnerability in Europe 2016

Climate change impacts on environmental systems
varies among the seas (Conversi et al., 2010). The
magnitude of future impacts on marine ecosystems
and the services they provide to humans is strongly
dependent on the future emissions scenario (Gattuso
et al., 2015).
By influencing a multitude of physical properties of
the oceans, climate change can cause abrupt changes
across whole ecological systems (EEA, 2015). Such
abrupt changes are called regime shifts and lead
to new regime conditions. Regime shifts are always
caused by multiple drivers lowering overall ecosystem
resilience. For example, the collapse of seagrass
populations can be caused by several key drivers such
as atmospheric CO 2 , disease, fishing, nutrient inputs,
sea level rise, sediment changes and temperature
changes (Rocha et al., 2014). It should be noted that
these drivers do not apply uniform pressure on the
different components of the marine ecosystems and
that climate change could exacerbate some of these
pressures.
Given the global extent of climate change, it can
cause continent-wide regime shifts. For example,
in the 1980s, the Mediterranean Sea underwent a
major climate‐induced change, which encompassed
atmospheric (e.g. changes in precipitation and
winter wind regimes), hydrological (e.g. changes
in circulation patterns) and ecological systems
(e.g. significant changes in copepod communities).
It appears that this event in the Mediterranean Sea
was linked to similar ecological shifts in the North
Sea, Baltic Sea and Black Sea, indicating that local
hydrography is linked to large-scale changes in the
northern hemisphere (Conversi et al., 2010). These
new conditions can last for decades and often cannot
provide the same services and benefits to humans
that were enjoyed under the previous ecological
regime. In some cases, there may be no return to the
previous state (Jackson et al., 2001; Weijerman et al.,
2005; Conversi et al., 2015; Mollmann et al., 2014).
Climate change‐induced regime shifts thus affect all
trophic levels of the food web and their associated
biogeochemical cycles. As a result, the overall
resilience of ecosystems decreases, making marine
ecosystems more vulnerable to other high-intensity
ecological stressors. Such high-intensity stressors
include the individual and cumulative impacts of
human activities (e.g. overexploitation, pollution and
the introduction of non-indigenous species).
Selection of indicators
The remainder of this section considers the following
physical and biological indicators of oceans and
marine ecosystems in Europe's seas:
• ocean acidification;
• ocean heat content;
• sea surface temperature;
• distribution shifts of marine species; and
• ocean oxygen content.
Of these indicators, the last one is less developed than
the others in terms of data coverage. Furthermore,
this section presents information about observed
and projected impacts of climate change on fish
and fisheries. This information is not suitable for
presentation as an EEA indicator owing to limited data
availability.
Uncertainties and data gaps
In general, changes related to the physical and
chemical marine environment are better documented
than biological changes. For example, systematic
observations of sea surface temperature began around
1880. More recently, these manual measurements have
been complemented by satellite-based observations
that have a high resolution in time and a wide
geographical coverage, as well as by Argo floats ( 46 ) that
automatically measure temperature and salinity below
the ocean surface. In contrast, the longest available
time series of plankton from the Continuous Plankton
Recorder (CPR) ( 47 ) is around 60 years. Sampling was
started in the North Sea in the 1950s and today a
network covering the entire North Atlantic Ocean has
been established.
Our understanding is improving of how climate
change, in combination with the synergistic impacts
of other stressors, can cause regime shifts in marine
ecosystems, but additional research is still needed to
untangle the complex interactions and their effects
upon biodiversity. Ecological thresholds for individual
species are still only understood in hindsight, i.e. once a
change has occurred.
( 46 ) http://www.argo.ucsd.edu.
( 47 ) https://www.sahfos.ac.uk/services/the-continuous-plankton-recorder.
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