Climate change: study maps those at greatest risk from cyclones and rising
seas
The first global study to identify populations at greatest risk from rising
sea levels and more intense cyclones linked to climate change
published this month in the peer-reviewed journal Environment and
Urbanization.
The research shows that 634 million people - one tenth of the global
population - live in coastal areas that lie within just ten metres above sea
level.
It calls for action to limit the effects of climate change, to help people
migrate away from risk and to modify urban settlements to reduce their
vulnerability. But it warns that this will require enforceable regulations
and economic incentives, both of which depend on political will, funding and
human capital.
Key findings of the study by Gordon McGranahan of the International
Institute for Environment and Development (UK) and his colleagues, Deborah
Balk and Bridget Anderson, at the City University of New York and Columbia
University, are that:
* Nearly two-thirds of urban settlements with more than 5
million inhabitants are at least partially in the 0-10 metre zone.
* On average, 14 percent of people in the least developed
countries live in the zone (compared to 10 percent in OECD countries).
* 21 percent of the urban populations of least developed
nations are in the zone (11 percent in OECD countries).
* About 75% of people in the zone are in Asia.
* 21 nations have more than half of their population in the
zone (16 are small island states).
* Poor countries - and poor communities within them - are most
at risk.
The study published on 14 April along with papers that focus on
specific cities, including Cotonou (Benin), Dhaka (Bangladesh), Mumbai
(India) and Shanghai (China).
"Urban development in the coastal zone brings multiple risks," says
McGranahan. "It exposes people to seaward hazards such as storms, flooding
and cyclones, and it can damage sensitive ecosystems including those such as
mangrove forests that protect the coastline."
"One in ten people, and one out of every eight urban dwellers, live on
the
coast no more than ten metres above sea level, but that number is
increasing," says McGranahan. "People are running towards risk,
particularly
in China but also in other parts of the world such as Bangladesh, where more
40% of the land area is within ten metres above sea level."
China's economic boom has been driven by policies that promote coastal
development and which have encouraged one of the largest coastward
migrations ever. The study says that unless action is taken that China's
economic success will be placed at risk.
Last month the Intergovernmental Panel on Climate Change's (IPCC) latest
report warned that sea levels could rise by tens of centimetres this
century, making coastal populations more vulnerable to flooding and storm
surges. It also predicted more intense tropical cyclones (typhoons and
hurricanes).
"The IPCC is aware that there are high population densities in coastal
areas, but it has not yet recognised the links to urbanisation, and the
implications for adaptation to climate change," says co-author Deborah
Balk,
the acting associate director of the Institute for Demographic Research at
the City University of New York.
The new study highlights the importance of "the three Ms":
mitigation,
migration and modification.
"It is too late to rely solely on a reduction in greenhouse gas
emissions to
mitigate climate change, although this is clearly an imperative," says
McGranahan. "Migration away from the zone at risk will be necessary but
costly and hard to implement, so coastal settlements will also need to be
modified to protect residents."
"Of the more than 180 countries with population in the low-elevation
coastal
zone, 130 of them - about 70% - have their largest urban area extending into
that zone," adds Bridget Anderson, research associate at Columbia
University's Center for International Earth Science Information Network.
"Furthermore, the world's large cities - those with more than 5 million
residents - have, on average, one-fifth of their population and one-sixth of
their land area within this coastal zone."
Many of the countries with the most people in the 0-10 metre zone are large
Asian nations with densely populated river deltas, while many nations with
the greatest proportion of their people in the zone are small island states.
"Climate change is not a natural disaster but has largely been caused by
wealthy countries emitting greenhouse gases during their industrialisation,"
says McGranahan. "Yet the poorest countries that have contributed least to
the problem are most vulnerable to its effects. It is therefore incumbent on
rich nations to help poorer ones to adapt to the changes ahead."
McGranahan and colleagues analysed the GRUMP (Global Rural-Urban Mapping
Project) databases of fine-scale information on population and urban extent
along with elevation data derived from NASA's Satellite Radar Topography
Mission, and World Bank data on national income.
"Carefully combining spatial data layers allows us to calculate the
distribution of each country's population and urban settlements by elevation
along a narrow coastal strip of land in most places," notes Balk.
"These
kinds of estimates are impossible to derive from national-level data."
"The ability to map both human activities and environmental conditions
globally has revolutionary possibilities - and is very timely given the
emergence of global environmental challenges such as climate change." -
IIED
More information:
 International Institute for Environment and Development
http://www.iied.org
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