Droughts and rising sea levels are impacts of climate change that will most affect Mediterranean basin

Human-induced climate change is causing a dangerous and generalized perturbation in nature and it is affecting the life of billions of people worldwide. The people and ecosystems with a lower capacity to deal with this situation are the most affected ones, according to the scientific community, as stated in the last report by the Intergovernmental Panel on Climate Change (IPCC), published yesterday. The scientific community warns that the world is facing several climate risks that we will experience over the next two decades, and which have caused, in the Mediterranean, a warming of 1.5ºC (above the global average, which is 1.1ºC).

If the emissions are not reduced over the next decades and the warming level set in the Paris Agreement (1.5º) is exceeded, there will be serious impacts, and some of them will be irreversible. The new report, written by the IPCC Working Group II, focuses on analysing the impact of the climate change in the natural ecosystems and the socioeconomic systems, as well as their vulnerability and adaption capacity. It also assesses the best strategies to reduce the impact of global change at different scales. This international team of experts counts with the participation of Jofre Carnicer, lecturer of Ecology at the Faculty of Biology, the Biodiversity Research Institute (IRBio) of the University of Barcelona and the Centre for Ecological Research and Forestry Applications (CREAF), the only expert in Catalonia —and one of the few researchers in Spain— to have taken part in this report. The report was approved on Sunday, February 27, 2022, by the 195 governments members of the IPCC in a virtual approval session that lasted two weeks, from February 14 to February 27. The final report is the second instalment of the IPPC's Sixth Assessment Report (AR6), which will be completed this year.

According to the scientific community, between 3.3 and 3.6 billion people live in a context which is highly vulnerable to climate change, almost half of humanity. Globally, the most vulnerable areas are Central Africa, Southeast Asia, and Central America, while, in the European continent, the most threatened region is the Mediterranean area. In this sense, the new report is clear: in order to prevent the growing loss of life, biodiversity and infrastructures from happening, we need to adopt ambitious measures to mitigate the climate change and adapt to climate change. Despite the continuous advances in local experiences that study how to reduce the negative impacts of climate change in different sectors (adaptation), the report reveals there is still a gap between total needs and pioneering actions that are progressively being implemented. The consequences of climate change are severe among those populations with a lower income and in certain geographical areas of the planet which are more vulnerable. Also, these are modulated by age and gender. The study highlights that the current economic development is unsustainable, and it is essential to consider the inclusive participation of all social actors, as well as equity and climate justice, to develop mitigation and adaption actions towards a sustainable and climate-resilient model.

"This report is a dire warning about the consequences of inaction", says Hoesung Lee, president of IPCC. "It shows that climate change is a serious and growing threat to our well-being and to maintaining a healthy planet", he says.

Jofre Carnicer, IPCC lead author of the chapters on Europe and the Mediterranean, is very clear: "The environmental cost of inaction is high, and the report concludes that action is needed before the opportunity window we have, which is only two or three decades, closes. Every action is relevant, whether at the governmental and regional level, in industries and sectorial activities, or in in changes to citizens' lifestyles, and these actions can progressively contribute to reducing warming and impacts in the coming decades and for generations to come". The report stresses the need to introduce deep and transforming changes in all the sectors of society and specially in those economic activities that generate emissions. "The costs of adapting to the impacts of climate change will be even higher if we do not implement drastic and decisive emission reductions over the next two decades that put us on a warming path below 2ºC", warns Jofre Carnicer, member of the Department of Evolutionary Biology, Ecology and Environmental Sciences.

Biodiversity on the edge

The summary of the IPCC report considers the vulnerability of humans and that of the ecosystems to be interdependent. Therefore, it puts emphasis on the current and future effects of climate change in biodiversity. More than 40,000 studies covering marine and terrestrial systems. Science says that increased heatwaves, droughts and floods are already exceeding the tolerance threshold of many plants and animals, which has caused, on the one hand, local extinctions of populations of some temperature-sensitive or low-mobility species, such as endemic and more specialist species; and on the other, mass mortality of species in habitats that are more vulnerable to heat stress, such as seagrass meadows and coral reefs. The report is supported by scientific studies that warn that more than 50% of the planet species have moved over the last years, either to northern latitudes or to higher altitude areas, to escape the rising temperatures.

Moreover, the document analyses the risk of extinction of more than 100,000 species for which we have scientific documentation. The results are worrying: "We can see that in warming trajectories above 1.5ºC, that is, without a drastic reduction of emissions over the next two decades, the risk of extinction increases in many taxonomic groups, mainly by more than 10% of the species", notes Jofre Carnicer. The report does not include results or information of species at a local level because each species has a unique ecology and each pattern is extremely complex, but it does highlight the first extinction documented of a mammal species: the mosaic-tailed mouse (Melomys rubicola), native to a low-altitude tropical island (Bramble Cay) near Papua New Guinea, which disappeared after its habitat was drastically reduced due to extreme climate impacts and the rising sea levels.

Adaptation measures to maintain biodiversity, whose services we absolutely depend on as a society, include the restoration of ecosystems, application of nature-based solutions and the increase of protected land. "The planet's natural areas need to be protected more consistently because we are dependent on the ecosystem services to maintain the climate security on the planet. The oceans and forests take 50% of our greenhouse emissions and contribute to regulating the temperature of the planet. The report confirms that an increase in climate impacts can cause declines in the efficiency of global CO2 absorption by the ecosystems and thus positively feedback warming", notes Jofre Carnicer. The report suggests moving from 16% of world protected areas —a figure agreed on in the world agreements on biodiversity— to the 30% or 50% by 2030. "The solutions that are based on protecting nature or restoring nature are important, but we need them to be accompanied first by drastic reductions of gas emissions in multiple sectors over the next decades", notes Carnicer.

A Mediterranean under asymmetrical risk

The Mediterranean is warming up faster than most areas of the world. The temperature has already risen by 1.5ºC, while the world average remains around 1.1ºC. There is a consensus that droughts will be a relevant risk in the Mediterranean. In this sense, predictions indicate a notable increase in droughts: for each degree the temperature rises, rains will be reduced by 4%, so that reductions of between 5% and 20% are predicted, depending on our capacity to reduce emissions.

In the Mediterranean, it is essential to tackle the use of water in agriculture to try to adapt to this drought and the temperature rise. Also, it is necessary to promote other agricultural methods that are more efficient and that keep soil humidity better, such as regenerative agriculture, which keeps the soil more fertile and richer in organic matter.

Moreover, the Mediterranean basin's vulnerability to climate change is very asymmetrical. The report reviews the Sustainable Developmental Goals in this area and it reveals that the indicators are extremely different between the southern and the northern shores of the Mediterranean basin. The southern shore features low rates of poverty, food security, access to renewable energies, water, education and health. This exposes the population of this area even more to the effects of climate change since they, for instance, have less resources to adapt to future impacts. "A clear example is the sea level rise in Egypt, a country with 103 million inhabitants. In the Nile Delta alone, more than 6.3 million people are expected to be seriously affected if the sea level rises above 80cm, a hypothetical scenario presented with today's greenhouse gas emissions", says Carnicer.

Food security

In Europe, agriculture will be a determining focus of impacts and adaptations to climate change. Science already shows that over the last fifty years, the loss of European crops due to droughts has tripled. Production losses up to 5% in the main crops (maize, wheat and rice) have been seen worldwide. Regarding the future, the Mediterranean region is expected to feature a decline of up to 17% in productivity, in the worst-case scenario. Also, globally, it is estimated that about the 10% of the arable land will not be able for agriculture due to the climate change in high warming scenarios. In addition, farm workers could be subject to 250 very hot days per year.

Although there are adaptation measures in agriculture, such as changes in the crop calendar, shifting crop areas to higher areas, or the use of species that are more resistant to salinity or water stress, the report documents that in high warming scenarios (>2ºC) some adaptation measures can be no longer effective and will not maintain the current food production.

Climate-resilient development

The current report states that the current human development is neither sustainable nor resilient to climate change. In this context, the study highlights the need for transformative actions, that drastically mitigate the emissions and the effects of climate change and enable the adaptation of the people and the land, with a special emphasis on the need for inclusive and equitable options. The document highlights the need for fair and inclusive governance schemes, where adaptation measures are taken considering the voice of all actors and providing co-creation activities of solutions in the different fields. Therefore, for instance it considers the knowledge of local and native populations as well as scientific knowledge. Last, the scientific community highlights the need for international cooperation and the collaboration of governments at all levels with communities, socially disadvantaged groups, civil society, educational bodies, scientific and other institutions, media, investors and businesses to facilitate more sustainable and climate-resilient activities.

IPCC: international science for the benefit of environmental policies

IPCC reports provide governments with data of great scientific interest, which can be used to design climate policies. They are also a key contribution to international agreements in order to cope with the climate change within the frame of the UN Framework Convention on Climate Change (UNFCCC).

Specifically, IPCC comprises three working groups: the Working Group I, which analyses the physical bases of climate change; Working Group II, which studies the impact, adaptation and vulnerability, and Working Group III, which focuses on the mitigation of climate change. Now, the new report by the Working Group II broadens the knowledge frame on climate change that was published by the Working Group I in August 2021, within the framework of the IPCC Sixth Assessment Report (AR6).

To write the new report, an international scientific team built by two-hundred experts —appointed by each country's government— worked together during the last seven years to gather as much science data as they could —more than 40,000 publications— on climate change problems. Then, the acquired knowledge was reviewed in several phase by the main international experts, as well as by the governmental interlocutors who develop public policies related to climate change. Last, the report was written gathering the most highlighted conclusions and it was presented publicly and open to the whole society.