The ecosystem services of Mediterranean forests are at risk if global temperatures rise more than 2°C

For the first time, the scientific evidence on how fire risk and ecosystem services in Mediterranean forests are affected by a global temperature increase or decrease above 2°C is reviewed.

Forests with temperate species –typical of areas with 4 seasons– are expected to experience a significant decline if the increase in the average temperature of the Mediterranean basin remains at the 2 degree threshold. However, if the thermometer rises above this limit set by the 2015 Paris Agreement, even species accustomed to drought, such as holm oak or white pine, will suffer the consequences and be compromised. This is one of the main conclusions of the study ‘Ecosystem Services provision by Mediterranean forests will be compromised above 2ºC warming’, published today in the scientific journal Global Change Biology, led by Alejandra Morán-Ordóñez, CREAF researcher and Forest Science and Technology Centre of Catalonia (CTFC) associate, and Aitor Ameztegui, researcher at the University of Lleida (UdL) and the Joint Research Unit CTFC-Agrotecnio, among others.

The study is the first systematic and quantitative review of the potential impacts of climate change on the provision of ecosystem services (benefits provided) and the risk of fire, both above and below the threshold of 2 degrees of temperature compared to pre-industrial levels, in the northern and southern Mediterranean countries.

If warming in the Mediterranean basin rises above 2°C, the numerous indicators on fire and climate risks increase by an average of 64%

It is also noted as a trend that, if the temperature rises above 2 degrees, indicators on fire and other climate-related risks increase by 64% in the Mediterranean territories. These indicators used to obtain this percentage are very diverse and include the Fire Weather Index, the number of hectares burned, the number of days with high fire risk, the number of days with prolonged drought and other climate-related risks, among many others.

The article published in Global Change Biology is part of a broader report by the MedECC project coordination team, which aims to assess the consequences of global warming and other anthropogenic change factors –e.g. land use change and overexploitation of resources– on ecosystem services in the Mediterranean. In this way, it seeks to complement the recent reports of the Intergovernmental Panel on Climate Change (IPCC) on Mediterranean geographic particularities with common climatic realities.

A small sea

"The Mediterranean is a small and relatively closed sea, which warms on average 20% faster than the global annual average temperature and with particularities that cannot be assimilated to the trends in the rest of Europe or Africa", according to Alejandra Morán-Ordóñez. This geographical reality conditions the increase in fire risks linked to the climate in this area.

The increase in droughts in the Mediterranean basin has many possibilities of transforming the forests: "we could reach the point where the forest absorbs a good proportion of the available water, so that less flows into the rivers and, therefore, less is available for human consumption and for maintaining sustainable ecological flows in the rivers," Morán-Ordóñez points out. In order to help identify possible scenarios, the paper published in Global Change Biology takes a quantitative approach related to ecosystem services.

"We summarise the scientific evidence on how climate change will affect the provision of wood, carbon fixation, mushroom production, etc., trying to put figures, with a clear desire to avoid catastrophism", according to Aitor Ameztegui. He adds that their intention is to "synthesise the scientific evidence on the impacts of climate change on Mediterranean forests, to provide information that will help to limit the effects of warming in the Mediterranean".

"The Mediterranean is a small and relatively closed sea, which warms on average 20% faster than the global annual average temperature and with particularities that cannot be assimilated to the trends in the rest of Europe or Africa"

ALEJANDRA MORÁN-ORDÓÑEZ, researcher at CREAF.

Aligned with big questions

The researchers' task has involved reviewing the 78 papers published to date on this issue, assessing current and future predictions (thanks to predictive modelling) of forests with respect to their capacity to adapt to and mitigate climate change. Given the difficulty of quantifying many impacts with common measures, Morán-Ordóñez and Ameztegui have promoted a systematic review, comparing the value of the future prediction with the current provision of each service, in order to provide a sense of the whole.

The question that the article seeks to answer is whether the works that evaluate the provision of services in the future detect the difference in possible behaviour above and below 2 degrees of temperature. And what situation is outlined if we are not able to stay below this limit.

 Reference:

The study ‘Ecosystem Services provision by Mediterranean forests will be compromised above 2ºC warming’, by Alejandra Morán-Ordóñez, Aitor Ameztegui, Lluís Brotons et al. is published on 7^th July 2021 in Global Change Biology.

doi https://doi.org/10.1111/gcb.15745