74
in this physically and chemically harsh environment, mangroves have developed
adaptations that allow them to cope with the high salinity, lack of oxygen, and tidal
turbulence. When you make your way into a mangrove forest, you are likely to
encounter many living things (Fig. 3.1). At low tide, mudskippers hop and colorful
crabs dance and wave their claws while waterfowl peck at them. If you are lucky,
you may observe a simultaneous spawning event of sea snails. At high tide, fish
swim swiftly through the intertwining roots of the partly submerged forest. If you
look up, you might see the brilliant blue of a kingfisher as it flies from branch to
branch. You might also notice monkeys watching you. Large mammals such as deer
and tigers also inhabit mangrove forests. Moreover, people who live around mangrove forests have been enjoying their blessings for countless years while handing
down from generation to generation their knowledge and philosophy of coexisting
with mangroves. Mangrove plants supply energy, in the form of food and other
materials, to these many living things, including human beings, through their production of organic matter. Another significant function of mangrove forest ecosystems is the absorption of carbon dioxide. In this chapter, I focus on carbon
sequestration in mangrove forests and examine the environmental factors that influence carbon regulation in mangrove ecosystems.
3.2 Global Mangrove Distribution
First, before discussing carbon sequestration itself, I would like to touch on the wide
distribution and diverse environmental settings of mangrove ecosystems. Given the
variety of mangrove forests around the world and their diverse features, it would be
surprising indeed if all mangrove ecosystems had the same carbon sequestration
ability.
If you want to see mangroves, two keys should guide your search. First, mangroves occur in mostly warm regions, the tropics and subtropics. More specifically,
they are confined to regions between about 35° north latitude and about 40° south
latitude: The most northerly mangroves are in Bermuda (32°20′N), and the most
southerly are found in Corner Inlet, Australia (38°45′S). These latitudinal limits
reflect water temperature, corresponding to the 20 °C winter water temperature isotherm (Duke 1992). My own research experience suggests that most mangrove
plants have difficulty surviving at water temperatures below 10 °C. Second, mangroves grow only in intertidal zones along coasts, where tidal fluctuations subject
them to repeated inundation and exposure. Numerous observations indicate that
mangroves grow mainly on tidal flats that lie above mean sea level. Although these
two environmental settings are key elements of mangrove distributions, it is actually
very difficult to obtain accurate data on mangrove distributions at the global scale,
because other factors also determine where mangroves grow, including local topography, micro-environmental characteristics, and human land use. Nevertheless,
several global distribution maps of mangroves have been drawn (Spalding et al.
1997, 2010: Giri et al. 2011). One map (Fig. 3.2), which can be downloaded from
T. Inoue
in this physically and chemically harsh environment, mangroves have developed
adaptations that allow them to cope with the high salinity, lack of oxygen, and tidal
turbulence. When you make your way into a mangrove forest, you are likely to
encounter many living things (Fig. 3.1). At low tide, mudskippers hop and colorful
crabs dance and wave their claws while waterfowl peck at them. If you are lucky,
you may observe a simultaneous spawning event of sea snails. At high tide, fish
swim swiftly through the intertwining roots of the partly submerged forest. If you
look up, you might see the brilliant blue of a kingfisher as it flies from branch to
branch. You might also notice monkeys watching you. Large mammals such as deer
and tigers also inhabit mangrove forests. Moreover, people who live around mangrove forests have been enjoying their blessings for countless years while handing
down from generation to generation their knowledge and philosophy of coexisting
with mangroves. Mangrove plants supply energy, in the form of food and other
materials, to these many living things, including human beings, through their production of organic matter. Another significant function of mangrove forest ecosystems is the absorption of carbon dioxide. In this chapter, I focus on carbon
sequestration in mangrove forests and examine the environmental factors that influence carbon regulation in mangrove ecosystems.
3.2 Global Mangrove Distribution
First, before discussing carbon sequestration itself, I would like to touch on the wide
distribution and diverse environmental settings of mangrove ecosystems. Given the
variety of mangrove forests around the world and their diverse features, it would be
surprising indeed if all mangrove ecosystems had the same carbon sequestration
ability.
If you want to see mangroves, two keys should guide your search. First, mangroves occur in mostly warm regions, the tropics and subtropics. More specifically,
they are confined to regions between about 35° north latitude and about 40° south
latitude: The most northerly mangroves are in Bermuda (32°20′N), and the most
southerly are found in Corner Inlet, Australia (38°45′S). These latitudinal limits
reflect water temperature, corresponding to the 20 °C winter water temperature isotherm (Duke 1992). My own research experience suggests that most mangrove
plants have difficulty surviving at water temperatures below 10 °C. Second, mangroves grow only in intertidal zones along coasts, where tidal fluctuations subject
them to repeated inundation and exposure. Numerous observations indicate that
mangroves grow mainly on tidal flats that lie above mean sea level. Although these
two environmental settings are key elements of mangrove distributions, it is actually
very difficult to obtain accurate data on mangrove distributions at the global scale,
because other factors also determine where mangroves grow, including local topography, micro-environmental characteristics, and human land use. Nevertheless,
several global distribution maps of mangroves have been drawn (Spalding et al.
1997, 2010: Giri et al. 2011). One map (Fig. 3.2), which can be downloaded from
T. Inoue