Saline Water in Wetlands and Aquifers

The highest degree of certainty about future climate change is that temperatures will increase.  One of the implications may be melting of glacial ice, leading to sea level rises and an increase in intense changes in the hydrological cycle, causing coastal hazards such as storm surges and an increase in erosion.  This may consequently have substantial impacts on coastal aquifers and wetlands.  Coastal aquifers may be intruded by saline water due to high levels of evapotranspiration, abstraction, sea level rises or storm surges (Ranjan et al 2006).    An increase in sea levels and storm surges may cause saline water to enter from coastal wetlands causing substantial long-term impacts on people, agriculture, fisheries, ecosystems and the economy.

Influences due to increases in salinity

Developing countries of high poverty in low coastal elevation areas are susceptible to sea level rises, as they are unable to adapt or protect themselves from these impacts.  Hence, an increase in salinity levels in the long run, may destroy natural ecosystems such as mangroves, which could act as a natural barrier protecting areas against extreme events, such as storm surges (Barbier 2015).  Many semi-arid and arid regions of Sub-Saharan Africa are reliant on groundwater resources for domestic use.  However, due to salinity intrusion, less freshwater will be available for cooking, drinking and sanitation, creating a decrease in livelihood (Barbier 2015).

Less wealthy households are highly reliant on agriculture and fisheries for their provision of food and income.   In Tanzania and Zanzibar around 34% of people are reliant on fisheries and 38% on farming, to provide an income for their families (Barbier 2015).  With an increase in sea-levels there may be a shift in fish population.  The destruction of near-shore ecosystems, such as mangroves and wetlands will destroy the natural habitat of some fish, forcing them to migrate.  Hence, decreasing fish availability for people (Barbier 2015).  Furthermore, many agricultural landscapes may inundate and crops may be destroyed, such as rice.  It is suggested that in Nigeria all agricultural produce will be destroyed due to sea inundation (Barbier 2015).   This is a concern as it may cause a poverty-environment trap (Figure 1).  A degradation in agriculture and fisheries may lead to more people searching for other types of occupations.  Therefore, the availability of labour will increase dramatically, leading to high unemployment rates and a high reliance on government benefits.

Figure 1: The Poverty- Environment Trap Cycle
Source: Barbier 2015

Impacts on groundwater quality

Conversely, there is high uncertainty on how groundwater quality may change in coastal Sub-Saharan African aquifers.  According to Ranjan et al 2006, groundwater levels may decrease by 0.002%.  As such, a low decrease in groundwater levels, may not be a substantial intrusion of sea-water in aquifers, suggesting minimal impacts to people who are highly reliant on groundwater resources.  However, this is variable on abstraction rates and the geology of an aquifer. 

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