Climate Change The 2015 Paris Agreement Thresholds And Mediterranean Basin Ecosystems

Given the importance of Mediterranean ecosystems being a hotspot for global biodiversity and provide many services to the population, including drinking water, flood protection, carbon storage and recovery, this further increase in temperature is essential. As a result of the Paris Agreement and the resulting climate discussion, the focus has been on two thresholds: limiting the average increase in global temperature to 2°C or the more ambitious 1.5°C. But what would these changes mean for different parts of the world? Researchers studied plant ecosystems in the Mediterranean and used pollen cores to create ecosystem models since the last great ice age. They then assessed the impact of four future climate scenarios, ranging from a rise of 1.5°C to more than 4°C. How different has this region been in the past and what changes can we expect in the future? This image shows the biomes modelled for each of the grid points on the land mass of the Mediterranean basin. The data comes from the BIOME4 model, which is run in two different ways. The first two were generated from the “reverse” mode, with pollen core data being input. The following five maps were generated in “Forward” mode, with climate data inserted to obtain biomtypes. The Holocene is known for its climatic stability. How is this reflected in this group? Comparing changes in average temperature and precipitation between 1990 and 2005 (fig.

1), our results showed that 50% of the wetlands studied experienced a temperature increase of more than 0.6 °C to reach a maximum of 1.1 °C and 70.6% of the sites (fig. 1a). Warming has occurred mainly in the south-eastern Mediterranean, where most of the unprotected sites are located at the same time (figs. 1 and S1). Our results also indicate a decrease in precipitation in the southeast over the years (Figure 1), which corresponds to an increase in drought episodes and a decrease in water availability in this region, as other studies have found (Mariotti et al. 2008). Kelley CP, Mohtadi S, Cane MA, Seager R, Kushnir Y (2015) Climate change in the fertile crescent and effects of the recent Syrian drought. Proc Natl Acad Sci 112:3241-3246. Gardner RC, Barchiesi S, Beltrame C, Finlayson CM, Galewski T, Harrison I, Paganini M, Perennou C, Pritchard D, Rosenqvist A, Walpole M (2015) State of the world`s wetlands and their services to people: a compilation of recent analyses. SSRN Scientific work. Social Science Research Network, Rochester. Schmeller DS, Julliard R, Bellingham PJ, Böhm M, Brummitt N, Chiarucci A, Couvet D, Elmendorf S, Forsyth DM, Moreno JG, Gregory RD, Magnusson WE, Martin LJ, McGeoch MA, Mihoub J-B, Pereira HM, Provença V, van Swaay CAM, Yahara T, Belnap J (2015) Towards a global terrestrial species monitoring program.

J Nat Conserv 25 (May): 5157. Mediterranean terrestrial ecosystems are sensitive not only to warming, but also to changes in water availability. Although changes in past precipitation and their projections for the future are more heterogeneous in space than temperature fields (7), in most scenarios, changes in these two areas will decrease water availability and cause losses of Mediterranean ecosystems and their biodiversity in the coming decades (8-10). During the Holocene (especially in the second half of this period) there were rainfall deficits, but unlike the situation in the twenty-first century, temperatures did not rise above the current average (fig. 1) (4). These periods of rainfall deficits [~6 to ~5.2, ~4.2 to ~4 and ~3.1 to ~2.9 Thousand years before the present (B.P. year)] have been identified as possible causes of the decline or collapse of civilization in the eastern Mediterranean (11-13). A recent study (14) attributed significant crop losses in Syria to two significant drought episodes in the Eastern Mediterranean (reduced by up to 30% during the 6-month winter season) and high temperatures (warming of 0.5° to 1.0°C on an annual average compared to the 20th century average) – in the eastern Mediterranean between 1998 and 2010.

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Tjip de Jong

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