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7.1 Introduction
7.1.1 The Menace of Ever-Increasing Atmospheric CO 2
Carbon dioxide (CO 2 ) and its dynamics in the natural ecosystems are perhaps the
most studied and discussed issues of the last few decades. Ever since the greenhouse
gas potential (GWP) of CO 2 , its rapid increase in concentration in the atmosphere
(mostly due to anthropogenic activities) and its contribution to global warming and
climate change were realized, quantification of the source and/or sink strength of
various ecosystems (both natural and man-made) became the ‘need of the hour’
(IPCC 2007). The partial pressure of CO 2 (pCO 2 ) in the pre-industrial era used to be
~280 μatm, which increased to ~367 μatm in 1999, ~379 μatm in 2005 (IPCC 2007)
and at present it has just crossed 400 μatm according to the observations made in
Mauna Loa Observatory, Hawaii. A group of scientists strongly believe that in near
future we can witness an atmosphere having double the CO 2 concentration than the
present levels (IPCC 2012). Owing to such predictions and the ongoing trends, it
has become imperative to understand the functioning and characteristics of various
crucial ecosystems found throughout the globe which has the potential to play a
significant role in maintaining the carbon equilibrium. In this regard, the importance
of terrestrial biomes like forest ecosystems is unambiguously appreciated.
7.1.2 The Role of Forests to Mitigate CO 2 Emission
Forests are usually a complex ecosystem by virtue of their variability in structure
and composition (Noe et al. 2011). The forest ecosystems have the potential to play
a decisive role in governing the atmospheric composition and in turn the global
climate, through exchanging trace gases between the biosphere and the atmosphere
(Magnani et al. 2007; Misson et al. 2007). Dixon et al. (1994) estimated forests to
represent a carbon pool of 1146 PgC shared by their above ground biomass (31%)
and by the soils (69%) mostly as soil organic carbon and belowground biomass;
however, recent estimates of Liu et al. (2015) showed that at present forest carbon
stock ranges between 652 and 952 PgC. Terrestrial gross primary production (GPP)
is at present known to be the largest global CO 2 flux [∼123 ± 8 Pg C year
−1
estimated by Beer et al. (2010); 107–152 Pg C year
−1
estimated by Campbell et al.
(2017)] which in turn drives several ecosystem functions (Reich 2010).
7.1.3 Mangroves and Their Specialty
Among the several types of forests found in the globe, mangroves are considered as
one of the most important forested ecosystems from the perspective of their carbon
sequestration potential and blue carbon standing stock (Pendleton et al. 2012). The
A. Akhand et al.
7.1 Introduction
7.1.1 The Menace of Ever-Increasing Atmospheric CO 2
Carbon dioxide (CO 2 ) and its dynamics in the natural ecosystems are perhaps the
most studied and discussed issues of the last few decades. Ever since the greenhouse
gas potential (GWP) of CO 2 , its rapid increase in concentration in the atmosphere
(mostly due to anthropogenic activities) and its contribution to global warming and
climate change were realized, quantification of the source and/or sink strength of
various ecosystems (both natural and man-made) became the ‘need of the hour’
(IPCC 2007). The partial pressure of CO 2 (pCO 2 ) in the pre-industrial era used to be
~280 μatm, which increased to ~367 μatm in 1999, ~379 μatm in 2005 (IPCC 2007)
and at present it has just crossed 400 μatm according to the observations made in
Mauna Loa Observatory, Hawaii. A group of scientists strongly believe that in near
future we can witness an atmosphere having double the CO 2 concentration than the
present levels (IPCC 2012). Owing to such predictions and the ongoing trends, it
has become imperative to understand the functioning and characteristics of various
crucial ecosystems found throughout the globe which has the potential to play a
significant role in maintaining the carbon equilibrium. In this regard, the importance
of terrestrial biomes like forest ecosystems is unambiguously appreciated.
7.1.2 The Role of Forests to Mitigate CO 2 Emission
Forests are usually a complex ecosystem by virtue of their variability in structure
and composition (Noe et al. 2011). The forest ecosystems have the potential to play
a decisive role in governing the atmospheric composition and in turn the global
climate, through exchanging trace gases between the biosphere and the atmosphere
(Magnani et al. 2007; Misson et al. 2007). Dixon et al. (1994) estimated forests to
represent a carbon pool of 1146 PgC shared by their above ground biomass (31%)
and by the soils (69%) mostly as soil organic carbon and belowground biomass;
however, recent estimates of Liu et al. (2015) showed that at present forest carbon
stock ranges between 652 and 952 PgC. Terrestrial gross primary production (GPP)
is at present known to be the largest global CO 2 flux [∼123 ± 8 Pg C year
−1
estimated by Beer et al. (2010); 107–152 Pg C year
−1
estimated by Campbell et al.
(2017)] which in turn drives several ecosystem functions (Reich 2010).
7.1.3 Mangroves and Their Specialty
Among the several types of forests found in the globe, mangroves are considered as
one of the most important forested ecosystems from the perspective of their carbon
sequestration potential and blue carbon standing stock (Pendleton et al. 2012). The
A. Akhand et al.