Sea-level rise does not happen in isolation (see Ta-
ble 6C.1 for interacting factors) and it is only one of a
number of changes that are affecting the world’s coasts.
For instance, under a positive sediment budget, coasts
may be stable or even grow, while under a negative
sediment budget, sea-level rise is exacerbating a situa-
tion that is already prone to erosion. Due to increasing
human activity in coastal zones and their catchments,
sea-level rise impacts are more often exacerbating an ad-
verse situation than not. This emphasizes the need to
analyse the impacts of sea-level rise within a framework
which addresses multiple stresses.
These natural system changes have many important di-
rect socio-economic impacts on a range of sectors. For
instance, flooding can damage key coastal infrastructure,
the built environment, and agricultural areas, while ero-
sion can lead to a loss of buildings with adverse conse-
quences on coastal communities and on sectors such as
tourism and recreation. As well as these direct impacts,
indirect impacts are also apparent, including impacts on
human health. For example, mental health problems in-
crease after a flood. Thus, sea-level rise has the potential to
produce a cascade of direct and indirect impacts through
the socio-economic system. The uncertainties around the
actual socio-economic impacts are also large, as impacts
will depend on the magnitude of changes to natural sys-
tems and on society’s ability to adapt to these changes.
Most existing studies examine exposure or potential
impacts – few consider the potential impacts while tak-
ing into account realistic assumptions about adaptation.
this would require significant investment and planning.
This is a complex issue to analyse as it requires integra-
Measures instituted to protect human safety may also
tion across the natural, engineering and social sciences.
exacerbate ecosystem impacts, and this needs to be tak-
The available analyses all suggest that the high value of
en into account. For example, building dykes can result
many coastal areas would make widespread adaptation
in the loss of salt marshes and mudflats
49
. Delivering
to sea-level rise an economically rational response in
effective adaptation will be challenging, especially in the
cost-benefit terms
47,48
. Following this logic, actual im-
poorer countries – and disasters can still occur in rich
pacts would be greatly reduced through adaptation, but
countries, as shown by Hurricane Katrina in 2005.
166 GLOBAL OUTLOOK FOR ICE AND SNOW