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NatRiskChange Project I9: Analysis of concurrent climate extremes driving land degradation and recovery in the Mediterranean regions

A combination of severe climate events in the form of low seasonal to annual precipitation occurring together with several high-intensity storms and high temperatures are known to have a particular severe impact on dryland ecosystems and their ecosystem functions, even though individual events involved may not be counted as extremes themselves. In the past, most analyses of climate and weather extremes typically tend to focus on only one of the climatic conditions; however, this univariate approach may underestimate the effects of concurrent and compound extremes on dryland degradation. Multivariate extreme events, i.e. extremes of two or more climate variables occurring simultaneously, are likely to impact dryland ecosystems greater than their univariate counterparts. The succession of these events is also likely to play a critical role on how likely an ecosystem will be able recover from previous detrimental events. However, concurrent, compound and succession quantities of and impact on dryland ecosystems such as the Eastern and Southern Mediterranean regions are unexplored both for past changes as well as for potential future changes.

To address this issue, this study will analyse changes in concurrences of several variables, such as meteorological and hydrological droughts, changing of onsets in typical winter and spring rainfall periods, flashfloods due to extreme rainfall and abnormal heavy or long rain periods, heatwaves or abnormal cold winters in relation to potential vegetation degradation for the last 40 years in selected catchments within eastern Mediterranean regions. The study will investigate changes in these variables and their concurrency using adapted statistical techniques for time series analysis on concurrency. 

Impact assessment of concurrent climate events and multiple stressors on plant fitness, growth and survival on dryland ecosystem will be carried out by using a combination of remotely sensed imagery (such as analysis MODIS-derived NDVI data using the BFAST method) and, where available, phenological time series. Phenological time series will give inside to the onset of different phenophases such as bud burst, fruit development and growth development, where as the remotely sensed imagery will give proxy for biomass development for the last 20 years.

Analyzing the historical changes in and impacts of concurrent climate extremes is critical to prepare for and mitigate the negative impacts of climatic change and land degradation in the future. Risk adaptation should not only rely on retrospective analysis but also on future new extremes or concurrency of extremes, in other words, new potentially harming combinations of climatological and ecological dynamics. A concurrency analysis of projected climate time series for the nearer future (2025-2075) is intended to draw new conclusions on how to manage dryland settings under impending future climate destabilisation.

Project coordination:

Johannes Vogel

Duration:

10/2018-09/2021

Collaboration partners:

Prof. Axel Bronstert, University of Potsdam

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