2
the Blue Carbon Report. We then try to provide a better understanding of the blue
carbon concept by explaining the important characteristics of blue carbon ecosystems. We use the carbon absorption process in seagrass meadows as an example to
illustrate important concepts.
1.1 Introduction
The first life on Earth evolved in the ocean. Living organisms first appeared in the
ocean about 3.5 billion years ago, and their metabolic activities eventually contributed to the exchange between oxygen and carbon dioxide concentrations in the
atmosphere. The metabolic functions of photosynthesis established an environment
where organisms could, through evolution, adapt to life on land. This gas exchange
was the first and can be considered as the most important ecosystem service provided by the ocean. Eventually, during the process of biological evolution over billions of years, the ecosystem diversified and its services multiplied. These changes
were accompanied by the emergence and extinction of numerous species. One
marine ecosystem service has been on-going from the first primitive life to the present: the absorption and sequestration of carbon dioxide in the ocean.
When people think of organisms that absorb carbon dioxide, many think of large
trees and the rich forests where these trees are found. Stark green blankets composed of terrestrial plants and extensive forests such as rainforests and boreal forests
come to mind. There is no doubt that these land plants assimilate carbon dioxide and
contribute to the mitigation of greenhouse gases.
A report that significantly modified this perception, however, was jointly published in 2009 by the United Nations Environment Program Planning Unit (UNEP),
the United Nations Food and Agriculture Organization (FAO), and the United
Nations Educational Science and Culture Organization (UNESCO) (Nellemann
et al. 2009; hereinafter this report is referred to as the UNEP report, using the acronym of the first organization). In the report, “Blue Carbon” is described as carbon
dioxide absorbed by living marine organisms. Actually, a little less than half of the
carbon dioxide biologically captured in the world is absorbed by terrestrial ecosystems, and marine ecosystems account for a majority of the carbon dioxide that is
absorbed. Furthermore, more than half of the carbon stored in the ocean is initially
absorbed in shallow coastal waters. The words “blue carbon”, which were used for
the first time in this report, characterize the carbon taken up by the ocean because of
the action of marine organisms.
Experts, especially in oceanography and biogeochemistry, initially recognized
the fact that marine organisms absorb an amount of carbon dioxide equivalent to
that absorbed by land plants. However, this fact has been hardly recognized by the
public. In addition, the UNEP report’s conclusion that most of the carbon dioxide
absorbed by the ocean is accumulated in shallow coastal areas was surprising, even
to research scientists. The UNEP report stimulated the initiation of blue carbon
M. Hori et al.
the Blue Carbon Report. We then try to provide a better understanding of the blue
carbon concept by explaining the important characteristics of blue carbon ecosystems. We use the carbon absorption process in seagrass meadows as an example to
illustrate important concepts.
1.1 Introduction
The first life on Earth evolved in the ocean. Living organisms first appeared in the
ocean about 3.5 billion years ago, and their metabolic activities eventually contributed to the exchange between oxygen and carbon dioxide concentrations in the
atmosphere. The metabolic functions of photosynthesis established an environment
where organisms could, through evolution, adapt to life on land. This gas exchange
was the first and can be considered as the most important ecosystem service provided by the ocean. Eventually, during the process of biological evolution over billions of years, the ecosystem diversified and its services multiplied. These changes
were accompanied by the emergence and extinction of numerous species. One
marine ecosystem service has been on-going from the first primitive life to the present: the absorption and sequestration of carbon dioxide in the ocean.
When people think of organisms that absorb carbon dioxide, many think of large
trees and the rich forests where these trees are found. Stark green blankets composed of terrestrial plants and extensive forests such as rainforests and boreal forests
come to mind. There is no doubt that these land plants assimilate carbon dioxide and
contribute to the mitigation of greenhouse gases.
A report that significantly modified this perception, however, was jointly published in 2009 by the United Nations Environment Program Planning Unit (UNEP),
the United Nations Food and Agriculture Organization (FAO), and the United
Nations Educational Science and Culture Organization (UNESCO) (Nellemann
et al. 2009; hereinafter this report is referred to as the UNEP report, using the acronym of the first organization). In the report, “Blue Carbon” is described as carbon
dioxide absorbed by living marine organisms. Actually, a little less than half of the
carbon dioxide biologically captured in the world is absorbed by terrestrial ecosystems, and marine ecosystems account for a majority of the carbon dioxide that is
absorbed. Furthermore, more than half of the carbon stored in the ocean is initially
absorbed in shallow coastal waters. The words “blue carbon”, which were used for
the first time in this report, characterize the carbon taken up by the ocean because of
the action of marine organisms.
Experts, especially in oceanography and biogeochemistry, initially recognized
the fact that marine organisms absorb an amount of carbon dioxide equivalent to
that absorbed by land plants. However, this fact has been hardly recognized by the
public. In addition, the UNEP report’s conclusion that most of the carbon dioxide
absorbed by the ocean is accumulated in shallow coastal areas was surprising, even
to research scientists. The UNEP report stimulated the initiation of blue carbon
M. Hori et al.