Climate change

The Mediterranean region: a climate change hot-spot.

The Mediterranean region has been referenced as one of the most responsive regions to climate change and was defined as a primary “Hot-spot” by Giorgi (2006), based on the results from global climate change projection scenarios. The last report from the International Panel on Climate Change (IPPC, 2013) highlights the Mediterranean as one of the most vulnerable regions in the world to the impacts of global warming. The context of global warming stresses the necessity to assess the possible consequences of climate change on this sensitive region which would become warmer and drier (IPCC 2007, 2013).

During the 20th century, air temperature in the Mediterranean basin was observed to have risen by 1.5-4°C depending on the sub-region. Over the same period and with clear acceleration since 1970, temperatures in south-western Europe (Iberian Peninsula, south of France) rose by almost 2°C. The same warming effect can also be seen in North Africa, albeit more difficult to quantify given the more patchy nature of the observation system. A key feature for the climate of the Mediterranean region is the presence of the Mediterranean Sea itself which represents an important source of energy and moisture to the atmosphere. Sea Surface Temperature (SST) anomalies govern, at least in part, air temperature and precipitation anomalies in the surrounding land areas (UNEP/MAP, 2016).

The costs associated with mismanagement of water resources can be very substantial. Over-abstraction is causing low river flows, lowered groundwater levels, and the drying-up of wetlands. All of these trends have detrimental impacts on freshwater ecosystems (EEA, 2015). Climate change is projected to increase water shortages, particularly in the Mediterranean region (EEA, 2012).

Sea level rise (SLR).

Based on the existing models available for assessment, the central values for projections of sea level rise by 2100 range from about 30 to 40 cm, and about 60% of this increase would be due to the thermal expansion of sea water. Climate change may also be seen through the evolution and impacts of sea level rise (SLR) with trends ranging from increases of over 6mm/yr and decreases going down to more than 4mm/yr in different regions of the basin, according to the EEA climate indicator (EEA-UNEP/MAP, 2014).  These variations have major impacts, especially on the southern areas of the region (IPCC, 2013). Such evolutions will be witnessed through high and low variations and very specific locations.

It is important to note that the steric contribution is only one of the components that might influence the sea level change in the Mediterranean Sea. There are other components that might determine the sea level trends in the basin, such as the melting of the continental ice sheets (Greenland and Antarctica) that, especially on the long term (centennial time scales), might become dominant. It should also be noted that in the case of SLR in the Mediterranean, scientific uncertainty is particularly high, as making multi-decadal regional projections for relatively small isolated and semi-isolated basins such as the Mediterranean is more complex than for the global ocean (EEA-UNEP/MAP, 2014 and UNEP/MAP, 2016). Nevertheless, the effect of SLR is considerable in most low-lying coasts of the Mediterranean basin where communities and infrastructure are typically located. In addition to the seawater expansion due to steric effect, coastal subsidence and global ocean level increase induced by continental glaciers melting (in Greenland and West Antartica) have to be considered as SLR components for the Mediterranean.

Climate Change related risks, vulnerabilities and impacts.

While determining tendencies and changes in the climatic system is quite delicate due to the multitude of factors that must be taken into account, the complexity of trying to identify the possible impacts of climate change is even greater, especially when considering uncertainties on regional and sub-regional trends. Indeed, these impacts are the result of confrontation between the major trends of climatic parameters and the specific conditions of the affected area, in other words the natural and manmade characteristics of the Mediterranean zone (UNEP/MAP, 2016).

Climate change is arguably one of the most critical challenges that the Mediterranean region is facing. The Mediterranean basin has been identified as one of the two most responsive regions to climate change globally. The IPCC Fifth Assessment Report considers the Region as “highly vulnerable to climate change”, also mentioning that it “will suffer multiple stresses and systemic failures due to climate changes”. The overall risks of climate change impacts can be reduced through mitigation, i.e. by limiting the rate and magnitude of climate change. However, even under the most ambitious mitigation scenarios, risks from adverse climate impacts remain, due to already locked-in climate change. Therefore, adaptation policies and measures anticipating a wide range of potential climate-related risks are essential.

Freshwater resources. The most critical impacts of climatic changes in the Mediterranean region are likely associated with the water availability. The whole region is already vulnerable to water scarcity and drought, in particular the South and East countries, while even in countries in the North, a growing percentage of water production is non-sustainable, leading to an over-exploitation of groundwater resources. A very critical situation under climate change in the region, with a reduction in precipitation and structural water shortages, is expected to affect 60 million people already from 2025 (Lionello et al. 2006). Another characteristic of water resources in the Mediterranean is their irregular geographic distribution: 71% are located in the North, 9% in the South and 20% in the Near East.

Most countries on the Southern and Eastern shores of the Mediterranean are already considered as facing chronic scarcity of water resources and the situation is expected to worsen in the future under the combined effect of increased demand for water and the projected impacts of climate change which

include declines in average rainfall and in total runoff, and depletion of groundwater resources. Coastal aquifers would become threatened by salinization due to rising sea levels and by overexploitation which declines their resilience to saline intrusion.

Moreover, despite a decrease in average precipitation, models foresee in the Mediterranean summers characterised by an increase in frequency of extreme daily precipitation. This tendency can lead to longer dry periods, interrupted by extreme intense precipitation, enhancing the risk of floods. The JRC PESETA II Project “Climate Impacts in Europe”, estimates that even in the 2oC scenario direct economic damages from river flooding in Southern Europe will increase from 0,67 to 1,19 billion euros per year in the 2080s. The rapidly growing non-agricultural water needs of many countries in the area can generally not be met by further exploitation of water resources except through either the development of expensive desalination facilities or the reallocation of water resources from agriculture. This could bring major social and political change and risk exacerbating existing inequalities and regional tensions.

Coastal systems and low-lying areas. Coastal zones, arguably the most appealing assets of the Mediterranean, are already exposed to significant pressures from land-based and marine pollution, urban development, fishing, aquaculture, tourism, damming, extraction of materials, and marine biological invasions. Climate change, and especially the major driver of sea level rise, is expected to significantly increase these pressures. In particular, many coastal systems will experience increased inundations and storm flooding, accelerated coastal erosion, seawater contamination of fresh groundwater, displacement of coastal lowlands and wetlands, encroachment of tidal waters into estuaries and river systems, possible loss of nesting beaches. More frequent and severe weather and climatic events will further enhance these phenomena, while in the longer term, changes in wind and wave patterns could interfere with sediment transport leading to greater erosion or accretion.

Coastal erosion will lead over time to the inland migration of the beaches of the Mediterranean with soft sedimentary coasts being more vulnerable than harder, rocky coastlines. River deltas, due to their particular topography, are particularly vulnerable to the impacts of erosion and inundation. Damming of rivers upstream no longer allows the normal circulation of sediment, which cannot reach the delta to consolidate it. At the local scale, possible impacts from sea level rise are also determined by other non-climatic factors such as the subsidence of coastal land, subsurface resource extraction, and tectonic movements. The JRC PESETA II Project “Climate Impacts in Europe”, estimates that even in the 2oC scenario the average annual costs from sea floods damage in Southern Europe will increase from 163 to 903 million in the 2080s.

Ocean systems. The Mediterranean Sea is among the richest in biodiversity of global importance, rich with endemism and autochthonous species. At the same time, it has unique marine features that make this region particularly vulnerable to climate change. The overall extent of water exchange is restricted due to the narrow connections with the Atlantic Ocean, the Red Sea and the Black Sea. In addition, due to the relatively small size of the basin, seawater in the Mediterranean can more easily heat up and evaporate, combined with hot, dry summers and low inflow from rivers. Increases in sea temperatures will alter distribution of species and foster the spread of warm water species into the Mediterranean, thus promoting the displacement of ecotypes and shifts in ecosystem functioning and ultimately lead to loss of species. The IPCC AR5 identified the Mediterranean Sea as one of the semi-enclosed seas with projected high rates of local extinction because land boundaries will make it difficult for species to move laterally to escape waters that may be too warm. Additionally, periods of extreme seawater temperature during heatwaves will contribute to mortality events that affect many invertebrate species as well as Posidonia meadows.

Another emerging climate-related threat to Mediterranean marine ecosystems, is ocean acidification, the phenomenon of shifting the chemical balance of seawater to a more acidic state (lower pH) due to increased CO2 concentrations in the sea as a result of increased CO2 concentrations in the atmosphere. Acidification is currently occurring at a geologically unprecedented rate, subjecting marine organisms to additional environmental stresses. According to the MedSEA project2, the acidity of Northwestern Mediterranean seawater has increased by 10% since 1995 and if current CO2 emission rates continue, it will increase another 30% by 2050 and 150% by 2100. Several planktonic organisms are affected by acidification with possible negative impacts on fish populations. Moreover, acidification also threatens iconic and invaluable Mediterranean ecosystem-building species (such as sea grass meadows, Coralligene reefs and Vermetid snail reefs) which create rich key habitats and homes to thousands of species, and also protect shores from erosion as well as offer a source of food and natural products to society.

Food security and food production systems. Agriculture absorbs over 80% and 60% of total water demand in the African and European countries surrounding the Mediterranean Sea, respectively. The general decrease in soil moisture and water availability in general, and the increase in the frequency and intensity of droughts as a result of climate change in the Mediterranean will increase the existing water-related stresses and have strong negative effects on crops and agriculture in general. The increased need for irrigation will be constrained by reduced runoff, reduced recharge of aquifers, and competition from other sectors, in particular human settlements and energy.

Climate change impacts also reverberate on the agricultural and food industry, driving major consequences on food insecurity and poverty:

  • In the absence of climate change, and with continuing economic progress, most regions are projected to see a decline in the number of people at risk of hunger by 2050. With climate change, however, the population living in poverty could be multiplied by 2 to 3 relative to a future without climate change, largely due to its negative impacts on incomes in the agricultural sector (FAO, 2016). Agriculture and the food sector at large have an important responsibility in climate change mitigation. Taken together, agriculture, forestry and land-use change account for about one-fifth of global GHG emissions (FAO, 2016).
  • Deep transformations in agriculture and food systems, from pre-production to consumption, are needed in order to maximize the co-benefits of climate change adaptation and mitigation efforts; the agriculture sectors have potential to limit their greenhouse gas emissions, but ensuring future food security requires a primary focus on adaptation (FAO, 2016).

Coastal Risk Index (CRI-MED) for the Mediterranean

The Regional Risk Assessment Map of coastal risk to climate and non-climate forcing, displays the result in terms of qualitative risk classes in the coastal zones investigated. The map shows the values of risk assumed by each location (cell) by applying the equation defined for the method CRIMED. Sites that assume “extremely high risk” values are indicated in red and in the context of the study these are defined as “hot-spots”.

CRI-MED is a spatial risk index, which combines variables (multiple data layers) representing different aspects of risk in such a way that coastal areas of relatively higher risk emerge from the integration of the variables. It creates an interface between theoretical concepts of risk and the decision-making process relating to disaster risk reduction. Based on a GIS application, CRI-MED provides relative hazard, exposure, vulnerability and risk maps of the Mediterranean region that allow researchers and policy-makers to identify coastal areas most at risk from coastal erosion and coastal flooding, the so-called “hot-spots”. Through the application of CRI-MED on 21 Mediterranean countries, coastal hot-spots are found to be predominantly located in the south-eastern Mediterranean region. Countries with the highest percentage of extremely high-risk values are Syria (30.5%), Lebanon (22.1%), Egypt (20.7%), and Palestine (13.7%). The CRI-MED method is intended as a scientific tool which produces easily understandable outcomes, to support international organizations and national governments to enhance and mainstream decision-making based on information that is accessible and useful. The definition of coastal hot-spots aims to support the prioritization of policies and resources for adaptation and Integrated Coastal Zone Management (ICZM). In particular, the resulting risk maps enable identification of suitable and less suitable areas for urban settlements, infrastructures and economic activities.

Beyond the north-south gradient in the Mediterranean, particularly vulnerable landscapes include deltas and coastal zones (vulnerable to sea-level rise), as well as rapidly growing cities without adequate infrastructure and institutions. In the Mediterranean regions, about 50% of the urban population lives less than 10m above sea level. Tourist destinations (concentrated along the coast) are vulnerable not only to sea-level rise but also to higher summer temperatures, which may turn tourists away toward more northern and cooler locations.

Figure 1.6
Coastal Risk Index (Satta et al., 2017)


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