In August 2019 in the port of Marseille.
The parking of cruise ships intensifies air pollution -
© Christophe Simon / AFP
The Mediterranean basin appears particularly vulnerable to the consequences of global warming, according to a study published by our partner The Conversation.
This risk is increased by air pollution, which is itself exacerbated during hot episodes in metropolitan areas such as Cairo and Marseille, in particular.
The analysis of this phenomenon was conducted by Joël Guiot, CNRS emeritus research director on climate change - Aix-Marseille University (AMU) and Wolfgang Cramer, CNRS research director - Mediterranean Institute of Biodiversity and Marine and Continental Ecology (IMBE), National Center for Scientific Research (CNRS).
The Mediterranean basin, which includes the sea and the countries bordering it, is regularly presented as a “hot spot” for climate change and biodiversity.
These upheavals cause, in interaction with pollution, the unsustainable use of land, water and the invasion of non-native species.
These are often underestimated risks for the populations and ecosystems of the area, which the recent MedEcc (Mediterranean Experts on Climate and environmental Change) report sets out to address.
Relief map of the Mediterranean basin © CIA / Joy / Wikimedia CC BY-SA
What exactly is this "hot spot"?
First of all, it cannot be said that the lands of the Mediterranean region have warmed faster than the others: its temperature has increased by 1.5 ° C compared to the pre-industrial period (1850-1900), therefore equal to the average of all the land areas of the globe.
On a planetary scale, climate change in these areas is accelerated compared to the oceans, whose global thermostat has been increasing by 0.2 ° C per decade since the end of the 1970s;
in this respect, the Mediterranean Sea figures clearly above (+0.3 to +0.4 ° C per decade since the end of the 1970s).
On the other hand, we cannot reduce the notion of “hot spot” of climate change to temperature alone, one factor of global change among others.
If we consider the cocktail of threats weighing down the Mediterranean basin and in particular its eastern and southern shores, the region appears particularly vulnerable.
"Global warming" dossier
Land and sea heat waves
This rise in temperatures has critical consequences in this region with a naturally hot climate.
During the day, especially in summer, it should reach + 3.3 ° C compared to the summers of the pre-industrial era for the "+ 2 ° C" scenario of the Paris Agreement;
this would significantly increase the intensity and frequency of heat waves.
Cities will experience heat peaks amplified by several degrees by mineral surfaces, with particularly significant risks for the health of the most vulnerable city dwellers - children, the elderly, the poor.
These risks are increased by air pollution in metropolises such as Cairo and Marseille, which is itself exacerbated during hot episodes.
The increase in maritime traffic in ports such as Marseille, to meet the growing demand for tourist cruises, has even greater repercussions on health as it generates peaks in sulfur dioxide and sulfur dioxide. nitrogen when summer temperatures reach their peak.
In the sea too, more intense and frequent heat waves have repercussions on biodiversity.
Ultimately, their effect on living things will be worsened by the acidification of the water, which absorbs more CO2 than the global ocean.
Tropical species arriving through the Suez Canal and the Strait of Gibraltar, and via the traffic of boats passing through one of the most heavily used routes in the world, tend to replace some native species, especially fish that are more adaptable. more easily at temperatures in the north of the basin.
Successions of droughts and floods
Coastal areas are both experiencing an increase in sea level which is currently accelerating (4.8 cm for 10 years).
It is expected to rise from 40 to 120 cm by 2100, depending on the different scenarios of greenhouse gas emissions.
The retreat of the coastline is also amplified by a drastic reduction in sediment input and by urbanization.
While this trend poses few problems in less populated regions or regions with high tides elsewhere in the world, it is very worrying on the Mediterranean coast, where populations, agrosystems, cultural heritage sites and coastal infrastructures have since established themselves. long on a coast with low tides.
The “Acqua Alta” of Venice in November 2019, with 190 cm of tidal peak, foreshadows what will happen more and more often around the Mediterranean during marine submersions.
Summary of the conclusions of the first report of Mediterranean experts on climate and environmental change (MedECC). Published in November 2020, it alerts policy makers and the public © MedECC (via The Conversation)
Precipitation undergoes a paradoxical development, with an increase in drought during the summer months and an increase in heavy rains and therefore the risk of flooding in winter.
Climate models consistently show an average decrease of 4% in the amount of precipitation per degree of global warming.
In an area where water resources are already insufficient for 180 million people (in the south and east of the basin), this shortage will increase, especially for the agricultural sector.
Especially since the total demand of the basin could increase by 22 to 74% by 2100 due to demographic changes, mass tourism and agriculture.
And the consequences will be dramatic in the south and east of the Mediterranean, whose climate is already described as arid, and which concentrates three quarters of the basin's population.
Our “Mediterranean” dossier
Threatened biodiversity
With its 25,000 plant species, 60% of which are endemic, the Mediterranean territory is also a hotspot for biodiversity.
It served as a refuge for plant and animal species during the last ice age, when the climate was significantly colder and the sea level 120 meters lower.
These ecosystems are today under the triple threat of drought, rising water levels and intensifying land use.
Many species are experiencing a sharp decline among insects, amphibians or reptiles.
In addition, there is climate change, pollution and overfishing, three phenomena that deeply affect Mediterranean marine ecosystems, which contain 18% of known species for an area of 0.82% of the global ocean.
Over the period 1950-2011, the Mediterranean thus lost 34% of fish species and the size of the catches decreased by 20 to 30%.
Forest fires due to heat waves, droughts and the abandonment of agro-pastoralism will be increasingly dramatic despite prevention efforts and response capacities.
The latter are effective for small and medium-sized fires, but much less for mega fires which will become more frequent.
Social and political instability
In addition to these natural and demographic characteristics of the Mediterranean basin, there is the social and political instability that agitates it, leading to economic losses, conflicts and significant suffering for the populations.
We can cite the increase in food prices in Tunisia which triggered the Arab Spring in 2011.
Although no causal link with climate change has been demonstrated, the transformations expected in the future are so strong that they will probably not be without impact on these instabilities and will require considerable adaptation efforts.
Economically, the region has a very strong dependence on mass tourism.
Before the Covid-19 health crisis, it hosted 30% of international holidaymakers in the world.
The sector faces a double threat of heat waves and environmental degradation on the one hand, and the necessary decarbonization of transport on the other.
The peak of water consumption for tourism coincides with that of agriculture which will require increasingly important irrigation, exacerbating conflicts of use.
The current crisis precipitates these evolutions and makes inevitable in the short term a paradigm shift of economic development based on perpetual growth, energy (mainly fossil fuel) and waste.
Remember that global warming is also an opportunity to progress towards lifestyles that are more respectful of nature.
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This analysis was written by Joël Guiot, CNRS emeritus research director on climate change - Aix-Marseille University (AMU) and Wolfgang Cramer, CNRS research director - Mediterranean Institute of Biodiversity and Marine and Continental Ecology (IMBE), National Center for Scientific Research (CNRS), with the kind contribution of Kasia Marini, scientific coordinator for MedECC at the Blue Plan (Regional Activity Center of the UNEP Mediterranean Action Plan).
The original article was published on The Conversation website.
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