Question

Which question has been addressed in this step?

Exploring risks: How will climate change affect land use and farmers' income in the Guadiana basin?

Why has this question been chosen?

• Impacts on crops, and especially on irrigated agriculture, can produce changes in land use and negative socio-economic consequences.

Which methods have been applied?

• An economic optimization model of farm-decision making is used in combination to the AquaCrop model and the WEAP model to analyze crop pattern changes and the socio-economic effects of climate change. Farmers choose the crops that maximize their expected utility subject to land, labor and water constraints. The models can simulate different agricultural and water management practices (at the farm and regional level) in response to changes in future climate conditions.
• The methodology includes a last stage consisting on the validation of results and evaluation of the models by stakeholders. Optimal farm plan and combination of crops given levels of future water availability.

Why have these methods been selected?

• Past experience of other research projects on the same basin. Model results are generally easily understood and well accepted by stakeholders.
• Models are user friendly.
• Good field data collection on farm financial and crop production activities, water use and water management practices.
• Regional climate model data also available.

What results have been obtained?

• Water demands are not fully satisfied in the period projected. The results of the WEAP simulations show that in the period 2011-2040 unmet demand is small. Water storage can mitigate the effects of dry climate periods. For that period, there is only one big drought, in which demand satisfaction is almost null. However, for the period 2041- 2070 water storage fails to mitigate the impacts of drought because of increased and generalized water scarcity. Specially, for the A2 scenario there are many years of large unmet demands, which correspond (figure 5) to many years of dramatic crop failures.
• Results show a shift from highly water demanding crops (rice, maize, tomato) to other crops with lower water requirements that become more profitable due to the increase of yields (broccoli, potato). Rice paddy-fields in the study region may disappear under severe dry periods
• Less modernized irrigation districts will be the most negatively economically affected by a reduction in water supply for agriculture.
• Increase of crop yields due to CO2 fertilisation seems to produce an overall increase of farm income at aggregate level.

Reflections on this step

• We would like to use further future climate scenarios to increase sampling of uncertainty space.
• Revision of crop model assumptions and, consequently, of the crop data introduced in the economic model for climate change scenarios is a next step. Stakeholders found these models very useful for the simulation of scenarios and found that results fit reality.