Climate change impacts and vulnerability in Europe 2016

Climate change impacts on environmental systems
mid‐20th century. The number of 'dead zones' globally
has increased from about 20 in the 1950s to about 400
in the 2000s (Diaz and Rosenberg, 2008).
Extensive areas with oxygen depletion or even anoxic
areas have been observed for decades in all European
seas (Map 4.1) (Diaz and Rosenberg, 2008; HELCOM,
2009; UNEP/MAP, 2013; Friedrich et al., 2014; Djakovac
et al., 2015; Topcu and Brockmann, 2015).
The largest area of human-induced hypoxia in Europe,
and in fact globally, is found within the Baltic Sea
(including the adjacent seas towards the North Sea).
The Baltic Sea is a shallow basin with restricted inlets,
meaning that the water has a high residence time,
making this water body prone to hypoxia. Hypoxic
areas in the Baltic Sea have increased more than
10‐fold, from 5 000 to 60 000 km 2 , since 1900, with
most of the increase happening after 1950 (Map 4.2).
This expansion is primarily linked to increased inputs
of nutrients from the land, but increased respiration
from higher temperatures during the last two decades
(since the early 1990s) has contributed to worsening
oxygen levels (Carstensen et al., 2014; Pyhälä et al.,
2014).
Oxygen depletion initially affects benthic organisms
(i.e. those living on or in the seabed). Benthic organisms
carry out important ecosystem functions, such as
bioturbation, bioirrigation and sediment nutrient
cycling. Benthic organisms also play a crucial role in the
marine food web, so reductions in benthic organisms
can have large impacts to commercial fisheries. The
loss of benthic macrofauna in the Baltic Sea (including
adjacent seas) as a result of hypoxia has been
estimated at 3 million tonnes or about 30 % of Baltic
secondary production (Karlson et al., 2002; Diaz and
Rosenberg, 2008).
Map 4.1
Distribution of oxygen-depleted 'dead zones' in European seas
-20°
-10°
40°
50°
Distribution of locations with
observed hypoxia
Classification
Celtic Sea
Greater North Sea
(incl. Kattegat and
the English Channel)
Baltic S
Eutrophic
Hypoxia (not specified)
Hypoxia (episodic)
Hypoxia (seasonal)
50°
Hypoxia (persistent)
Regional seas
ay
a a
Bay of Biscay and the Iberian Coast
Black Sea
Adriatic Sea
40°
Western
editerranean Sea
M edite
0 500 1000 1500 km
ranean Sea
Ionian
and the C
Mediterrane
a
tral
a
A ean
Levanti Sea
40°
Note:
Circles depict scientifically reported accounts of eutrophication-associated 'dead zones'. The area covered by 'dead zones' is not
presented, as such information is not generally available.
Source: Adapted from Diaz and Rosenberg, 2008.
120 Climate change, impacts and vulnerability in Europe 2016 | An indicator-based report