Ecosystem Services

Box 3: An investigation of CO2 uptake in marine ecosystems
In their study, Gundersen et al. (2011) estimated the existing and potential future distribution of kelp
and other ecosystems by evaluating different threat factors. The total existing area for L. hyperborea
and S. latissima along the Norwegian coast was estimated to 8,000 km2 (80 mill tons). The total area
loss due to sea urchins (Box 1) and fouling by filamentous algae (Box 2) was estimated as 2,000 km 2
(20 mill tons) and 7,800 km 2 (78 mill tons), respectively, and interpreted as a potential increase in area
if the threat factors would disappear. If all kelp forest fully recovers, the biomass will increase from 80
to 178 mill tons. This means increased yearly production of 98 mill tons (123%) per year. Today’s standing
biomass will bind up to 29 mill tons CO2. But if all kelp forest recovers during the next 20–40 years
that will bind up to 65 mill tons CO2, i.e. a gain of 36 mill tons bound CO2. This will be a one-time
happening when the sea floor regrows with kelp forest.
Also, a conservative (3% sequestrated – light green line in the figure below) and a moderate (8%
sequestrated – dark green line in the figure below) scenario for potential gain from sedimentation of
kelp material showed that 0.9 and 2.3 mill tons will be deposited every year, respectively, assuming
today’s production. These numbers will increase by 1.1 and 2.9 mill tons CO2 per year, respectively, if
the kelp forests grows back. An intact kelp forest would have, through the last 40 years, stored about
150 mill tons CO2 more in the oceans (due to increased amounts of standing kelp forest and 8% accumulation
of yearly production).
Figure 9: Estimated sequestration of CO2 from Norwegian kelp forests, given two different regrowth
scenarios, a moderate (8%) and a conservative (3%) one
Source: Gundersen et al. (2011).
Ecosystem Services 47