36
2 Coral Reef Ecosystem
2.5.2.2 Global Disturbances
Local threats weaken corals, thus reducing their resilience to global stresses (Carilli
et al. 2009).
Global climate change and disease, ocean acidification, habitat destruction, pollution from coastal development and anthropogenic threats, deteriorating water quality
in coastal environment related to land use changes in the catchment basins, and
heavily populated areas have been associated with the global decline of the coral reef
ecosystems (Hoegh-Guldberg 1999; Hughes et al. 2003; Pandolfi et al. 2003; Prouty
et al.2008; Ateweberhan et al. 2013; Bielmyer-Fraser et al. 2018). The coexistence
of these disturbances together have led to the destruction of coral reef ecosystems.
The following discusses how climate change in association with other factors
influences the coral reef ecosystems.
Climate Change Implications on Coral Reefs
Climate change relates to the change in the state of the climate, identified by changes
in the mean and/or variability of its properties and that, which persists for an extended
period. The change in climate over time could be due to natural variability or as a result
of human activities. Greenhouse gases (GHGs), namely carbon dioxide, methane,
and nitrous oxide are the driving force of climate change. These gases allow some
of the heat from the sun to be absorbed by the land and ocean, thus keeping the earth
within a stable temperature range comfortable for plants and animals, a phenomenon
called the greenhouse effect. Greenhouse effect is important for the existence of life
on earth; for without it the earth’s global temperature would be −18 °C.
Ever since the industrial revolution, human activities have increased the concentration of GHGs in the atmosphere (IPCC 2007, 2013). Increased concentrations of
GHGs cause climate change by trapping heat reflected from the land and ocean and
preventing it from leaving the Earth’s atmosphere. The trapped heat makes air and
water temperatures warmer than usual and hence leads to global climate change. EPA
(2016) reported that average seawater temperatures have risen at a rate of 0.07 °C
per decade over the past century.
The ocean, being the most important component of the climate system, is intrinsically linked to the atmosphere via gas exchange, heat transfer and biogeochemical
cycles. This warmer air and ocean surface temperature has fatal impact on corals.
It contributes to coral bleaching events and alters the ocean chemistry. Increase in
ocean surface temperatures causes zooxanthallae to be expelled from corals, making
them turn white. Marques et al. (2019) highlighted that tropical coral reefs are
mostly vulnerable to climate change. Furthermore, global disturbances associated
with climate change exacerbates acute and chronic local stressors from declining
water quality and overexploitation of key species, to driving reefs towards the tipping
point for functional collapse (Hoegh-Guldberg et al. 2007; Dalton et al. 2020).
Being a greenhouse gas, CO 2 has directly influenced the global temperature and
also has been absorbed by the ocean where it is being consumed by autotrophic
2 Coral Reef Ecosystem
2.5.2.2 Global Disturbances
Local threats weaken corals, thus reducing their resilience to global stresses (Carilli
et al. 2009).
Global climate change and disease, ocean acidification, habitat destruction, pollution from coastal development and anthropogenic threats, deteriorating water quality
in coastal environment related to land use changes in the catchment basins, and
heavily populated areas have been associated with the global decline of the coral reef
ecosystems (Hoegh-Guldberg 1999; Hughes et al. 2003; Pandolfi et al. 2003; Prouty
et al.2008; Ateweberhan et al. 2013; Bielmyer-Fraser et al. 2018). The coexistence
of these disturbances together have led to the destruction of coral reef ecosystems.
The following discusses how climate change in association with other factors
influences the coral reef ecosystems.
Climate Change Implications on Coral Reefs
Climate change relates to the change in the state of the climate, identified by changes
in the mean and/or variability of its properties and that, which persists for an extended
period. The change in climate over time could be due to natural variability or as a result
of human activities. Greenhouse gases (GHGs), namely carbon dioxide, methane,
and nitrous oxide are the driving force of climate change. These gases allow some
of the heat from the sun to be absorbed by the land and ocean, thus keeping the earth
within a stable temperature range comfortable for plants and animals, a phenomenon
called the greenhouse effect. Greenhouse effect is important for the existence of life
on earth; for without it the earth’s global temperature would be −18 °C.
Ever since the industrial revolution, human activities have increased the concentration of GHGs in the atmosphere (IPCC 2007, 2013). Increased concentrations of
GHGs cause climate change by trapping heat reflected from the land and ocean and
preventing it from leaving the Earth’s atmosphere. The trapped heat makes air and
water temperatures warmer than usual and hence leads to global climate change. EPA
(2016) reported that average seawater temperatures have risen at a rate of 0.07 °C
per decade over the past century.
The ocean, being the most important component of the climate system, is intrinsically linked to the atmosphere via gas exchange, heat transfer and biogeochemical
cycles. This warmer air and ocean surface temperature has fatal impact on corals.
It contributes to coral bleaching events and alters the ocean chemistry. Increase in
ocean surface temperatures causes zooxanthallae to be expelled from corals, making
them turn white. Marques et al. (2019) highlighted that tropical coral reefs are
mostly vulnerable to climate change. Furthermore, global disturbances associated
with climate change exacerbates acute and chronic local stressors from declining
water quality and overexploitation of key species, to driving reefs towards the tipping
point for functional collapse (Hoegh-Guldberg et al. 2007; Dalton et al. 2020).
Being a greenhouse gas, CO 2 has directly influenced the global temperature and
also has been absorbed by the ocean where it is being consumed by autotrophic