Sustainable Land Management potential for climate change adaptation in Mediterranean environments: a regional scale assessment

This presentation is about a model study on the potential of sustainable land management to mitigate the negative effects of climate change in a large-scale semi-arid catchment in SE Spain

The segura catchment is located in SE spain and can be characterized as a semi-arid catchment with an average yearly precipitation sum of 360 mm. A total of 33 reservoirs are located in the catchment, which are mainly used for irrigation and drinking water supply. Agriculture covers around 50% of the catchment. The main crop types are cereals, almonds and fruit trees

We applied the SPHY model, which is a hydrological model coupled with the MUSLE equation and included a transport capacity formula in the channel cells. We applied the model to a reference and 4 future scenarios, forced with data from 9 climate models. The most important climate change signal is the increase in extreme precipitation and a decrease of precipitation frequency

But more importantly, an increase in extreme precipitation will lead to an increase in surface runoff and soil erosion. At the catchment scale, this results in an increase in discharge and sediment yield at the reservoirs. In this presentation I will focus on adaptation measures to mitigate these effects

Sustainable land management is a promising technique to increase soil moisture and decrease soil erosion and surface runoff and mitigate climate change effects

Our study aims to upscale the application of SLM to all orchards in the catchment and to asses the catchment scale effect of SLM on water availability and soil erosion under current and future climate conditions

We implemented adaptation measures in areas covering cereals and tree crops (32% of the catchment). We applied two types of SLM: reduced tillage for cereals and reduced tillage plus organic matter amendment for tree crops. And applied changes to these variables: soil organic matter, bulk density, the MUSLE C-factor and the crop coefficient

First I will present the results of the soil erosion as calculated by the MUSLE equation, which is mainly forced by the surface runoff generated by the hydrological model. These two maps show the specific sediment yield for the reference scenario, without and with sustainable land management. It clearly shows that SLM is able to decrease soil erosion

When we look more specifically to the landuse classes we see that in the baseline scenario without SLM the agricultural landuses account for most of the soil erosion in the catchment. With SLM soil erosion most notably decreases for these two landuse classes, with a decrease of around 65%

These two maps show the change in soil erosion under climate change, with respect to the reference scenario. When we only consider climate change we see that soil erosion increases in almost all the catchment. With SLM implemented, in large parts of the catchment the specific sediment yield becomes similar to the reference scenario, where change is 0

When we focus on the landuse classes, we see the same pattern as in the previous slide, with a decrease for cereals and tree crops, both showing a net decrease with respect to the reference scenario

So what is the impact at the catchment scale? Both in the reference scenario and in the future scenario we observe a decrease of sediment yield when SLM is implemented, of around 4%. The impact at the catchment scale is much smaller than at the field scale

This figure summarizes the field scale effect of the impact of climate change, it shows a decrease in soil water content and an increase in soil erosion and discharge

When SLM measures are implemented we observe an increase in soil water content with respect to the reference scenario. A similar observation is made for the surface runoff which decreases and is in part responsable for the decrease of soil erosion at field scale. Therefore we conclude that SLM can significantly mitigate the negative effects of climate change at the field scale

However, at the catchment scale the effects are less pronounced, where sediment yield still increases with respect to the reference scenario. We conclude that SLM can mitigate the catchment scale effect of climate change by around 4%

Thanks you for your attention

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