147
ability of corals to produce their skeletons – will result in more prolonged episodes
of bleaching and increased mortality. Veron et al. (2009) estimate that by the 2030s
coral reefs could very well be in severe danger throughout the world, which could
create many problems for small island nations, given the reduction in sediment supply that this would represent. Given that these islands are geomorphologically very
dynamic, it is unlikely that they would disappear (Kench et al. 2009, Webb and
Kench 2010), though this could lead to greater damage due to high waves and the
need for substantial adaptation strategies. Nevertheless, evidence proves that it is
indeed possible for coastal communities to adapt to changes in sea levels of less
than 1 m, even if those changes happen quickly (Jamero et al. 2016).
However, when looking at a time scale of several centuries, the situation changes.
Sea level rise will not stop by the year 2100, and it would be increasingly difficult
for the inhabitants of small islands to adapt to changing water levels if all the coral
dies. This could eventually lead to societal collapse in the islands, forcing their
inhabitants to migrate (Yamamoto and Esteban 2014, 2016).
When looking at a longer time frame, it is clearly possible that coral communities will somehow adapt to these new changes (through the recruitment of new,
better-adapted species, Kench et al. 2009), and there is evidence that coral reefs
have adapted in the past to changing conditions (Kench et al. 2009). The Census of
Marine Life (2010) found relics of cold water corals off Africa’s Mauritanian coast
extending over 400 km in waters 500 m deep in one of the world’s longest reefs.
This highlights how corals have continuously evolved to adapt to changing ocean
conditions, and this will likely continue to happen in the future, though the time
frames involved are unclear. From an evolutionary point of view, coral diversification has occurred in pulses, and mass extinctions have caused bottlenecks in the
evolution of corals (Simpson et al. 2011). It is thus possible that major increases in
coral mortality also retard the time it takes the species to re-adapt to the new environmental conditions, as a less diverse coral population has less of a genetic base
from which to re-adapt. However, such evolution may already be taking place, and
some evidence indicates that certain species around the Persian/Arab Gulf may have
adapted or evolved to withstand higher sea temperatures, perhaps as much as 35 °C,
that would normally prove fatal to corals elsewhere (Hume et al. 2016).
Researchers in Japan have also stated that there is large scale evidence that several major coral species have begun spreading polewards at speeds of up to 14 km/
yr. (Yamano et al. 2011), showing how species can also adapt by moving to other
areas of the planet where they find more favourable conditions. Thus, these areas
may serve as a refuge for tropical corals in an era of global warming and could later
move towards the equator again if and when temperatures return to their present
values. One absolute limiting condition to this shifting of species towards the poles
may be acidity, as corals stop growing in pH concentrations of 7.7 or lower
(Fabricious et al. 2011), although it appears that some coral species can survive in
conditions of higher acidity. It thus appears that corals could somehow adapt to a
changing environment (by evolutionary or migration modes), assuming that this
lower level of ocean acidification is not reached. This adaptation happens even with
7 Time-Scale in Framing Disaster Risk Reduction in Sustainability
ability of corals to produce their skeletons – will result in more prolonged episodes
of bleaching and increased mortality. Veron et al. (2009) estimate that by the 2030s
coral reefs could very well be in severe danger throughout the world, which could
create many problems for small island nations, given the reduction in sediment supply that this would represent. Given that these islands are geomorphologically very
dynamic, it is unlikely that they would disappear (Kench et al. 2009, Webb and
Kench 2010), though this could lead to greater damage due to high waves and the
need for substantial adaptation strategies. Nevertheless, evidence proves that it is
indeed possible for coastal communities to adapt to changes in sea levels of less
than 1 m, even if those changes happen quickly (Jamero et al. 2016).
However, when looking at a time scale of several centuries, the situation changes.
Sea level rise will not stop by the year 2100, and it would be increasingly difficult
for the inhabitants of small islands to adapt to changing water levels if all the coral
dies. This could eventually lead to societal collapse in the islands, forcing their
inhabitants to migrate (Yamamoto and Esteban 2014, 2016).
When looking at a longer time frame, it is clearly possible that coral communities will somehow adapt to these new changes (through the recruitment of new,
better-adapted species, Kench et al. 2009), and there is evidence that coral reefs
have adapted in the past to changing conditions (Kench et al. 2009). The Census of
Marine Life (2010) found relics of cold water corals off Africa’s Mauritanian coast
extending over 400 km in waters 500 m deep in one of the world’s longest reefs.
This highlights how corals have continuously evolved to adapt to changing ocean
conditions, and this will likely continue to happen in the future, though the time
frames involved are unclear. From an evolutionary point of view, coral diversification has occurred in pulses, and mass extinctions have caused bottlenecks in the
evolution of corals (Simpson et al. 2011). It is thus possible that major increases in
coral mortality also retard the time it takes the species to re-adapt to the new environmental conditions, as a less diverse coral population has less of a genetic base
from which to re-adapt. However, such evolution may already be taking place, and
some evidence indicates that certain species around the Persian/Arab Gulf may have
adapted or evolved to withstand higher sea temperatures, perhaps as much as 35 °C,
that would normally prove fatal to corals elsewhere (Hume et al. 2016).
Researchers in Japan have also stated that there is large scale evidence that several major coral species have begun spreading polewards at speeds of up to 14 km/
yr. (Yamano et al. 2011), showing how species can also adapt by moving to other
areas of the planet where they find more favourable conditions. Thus, these areas
may serve as a refuge for tropical corals in an era of global warming and could later
move towards the equator again if and when temperatures return to their present
values. One absolute limiting condition to this shifting of species towards the poles
may be acidity, as corals stop growing in pH concentrations of 7.7 or lower
(Fabricious et al. 2011), although it appears that some coral species can survive in
conditions of higher acidity. It thus appears that corals could somehow adapt to a
changing environment (by evolutionary or migration modes), assuming that this
lower level of ocean acidification is not reached. This adaptation happens even with
7 Time-Scale in Framing Disaster Risk Reduction in Sustainability