Agriculture Reference
In-Depth Information
Scientists have found that oceans are able to
absorb some of the excess CO 2 released by
human activity. This has helped keep the planet
cooler than it otherwise could have been had
these gases remained in the atmosphere.
However, the additional excess CO 2 being
absorbed is also resulting in the acidifi cation of
the oceans: When CO 2 reacts with water, it pro-
duces a weak acid called carbonic acid, changing
the sea water chemistry. As the Global
Biodiversity Outlook report explains, the water is
some 30 % more acidic than preindustrial times,
depleting carbonate ions - the building blocks for
many marine organisms.
In addition, “concentrations of carbonate ions
are now lower than at any time during the last
800,000 years. The impacts on ocean biological
diversity and ecosystem functioning will likely to
be severe, though the precise timing and distribu-
tion of these impacts are uncertain.”
Although millions of years ago CO 2 levels
were higher, today's change is occurring rapidly,
giving many marine organisms too little time to
adapt. Some marine creatures are growing thin-
ner shells or skeletons, for example. Some of
these creatures play a crucial role in the food
chain and in ecosystem biodiversity.
Some species may benefi t from the extra car-
bon dioxide, and a few years ago, scientists and
organizations, such as the European Project on
Ocean Acidifi cation, formed to try to understand
and assess the impacts further.
One example of recent fi ndings is that a tiny
sand grain-sized plankton responsible for the
sequestration of 25-50 % of the carbon the oceans
absorb is affected by increasing ocean acidifi ca-
tion. This tiny plankton plays a major role in
keeping atmospheric CO 2 concentrations at much
lower levels than they would be otherwise so large
effects on them could be quite serious.
Other related problems reported by the Inter
Press Service include more oceanic dead zones
(areas where there is too little oxygen in the sea to
support life) and the decline of important coastal
plants and forests, such as mangrove forests that
play an important role in carbon absorption. This is
on top of the already declining ocean biodiversity
that has been happening for a few decades now.
Scientists now believe that ocean acidifi cation
is unparalleled in the last 300 million years, “rais-
ing the possibility that we are entering an
unknown territory of marine ecosystem change.”
4.14
Glacier Retreat
and Disappearance
The continued retreat of glaciers will have a num-
ber of different quantitative impacts. In areas that
are heavily dependent on water runoff from gla-
ciers that melt during the warmer summer months,
a continuation of the current retreat will eventu-
ally deplete the glacial ice and substantially
reduce or eliminate runoff (Fig. 4.12 ). A reduction
Fig. 4.12 Left : Milk Lake Glacier in 1988 clinging to the slope above the greenish lake. Right : Milk Lake in 2009, the
glacier now entirely gone
 
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