Page 26 - FAO-IPCC Expert meeting on climate change

Direct climate impacts on land-ecosystems and food provision
Rising sea levels threaten coastal soil with large deltas in Asia and Egypt particularly vulnerable. Saline water intrusion damages soils in coastal areas and the combination of climate warming and increasing irrigation demand will negatively impact on the quality of water.
The above interactions between climate, soil and land use demand the integration of soil status into the yield gap analysis. Typically this has not been done, though a few studies are starting to fill this gap. In particular, a recent study from China assesses the role of inherent soil productivity (i.e. crop yield gap analysis) in tandem with crop management and climate variables. Another study, undertaken by the International Institute for Applied Systems Analysis, indicates that in the absence of land degradation within the equation, crop yields in temperate regions, such as Germany, improve by 13 percent owing to a global warming of 2 oC. When land degradation is taken into account, however, no significant yield improvement is observed.
1.2.2 Climate, hydrological cycle and water scarcity
Approximately 80 percent of the world’s population suffers, to some degree, from water scarcity and many basins around the world are now considered hotspots and water stressed. Climate-induced changes in precipitation directly affect the amount of water entering water basins. Variations in temperature, radiation, humidity and wind speed
affect evapotranspiration, resulting in dryer river basins. Most climate change projections show a highly variable
spatial distribution of rainfall, with some regions as beneficiaries while others expected to have decreasing rainfall. Moreover, rainfall patterns are predicted to become more variable and extreme. Rising temperatures and enhanced CO2 concentration are anticipated to raise the level of evapotranspiration to some extent across most latitudes, especially in the northern latitudes.
More intense rainfall indicates increasingly frequent streamflow runoffs and less filtration and groundwater refill.
More water is flowing into rivers, but over shorter periods, leading to a greater variance in river regimes, which may have an impact on freshwater fisheries. Changes in snow melt timings as a result of rising temperatures also affect hydrological regimes, exacerbate the relationship between freshwater and groundwater and contribute to water quality degradation.
Modelling the hydrological impacts of climate change remains a challenge owing to the poor quality of water resource data. To date, only scattered observations at particular locations are available, often in the form of intermittent hydrological data series and with incomplete estimates, making it difficult to adequately create a methodology for the construction, calibration and validation of hydrological models. Modelling ground water is even more difficult and often ignored in these models. Given that groundwater is critically important for agricultural water supplies in many parts of the world, this absence causes a serious limitation. A further climate modelling challenge with hydrology is the non- matching scale between local and global. Since AR5, most regional studies project a decrease in water availability as a result of climate change well into the future. Projected food demand increases imply increased demand for irrigation, but global projections based on water supply offer divergent outcomes and irrigation acreage may decrease because
of reduced supply.3 In hotspot regions with acute water scarcity, reduced freshwater in areas that are currently irrigated may indicate that irrigation has to be abandoned altogether.
1.2.3 Climate impacts on ecosystem services: the case of pollinators
Over three-quarters of the world’s leading crops rely in part on pollination, with pollinators playing an essential role in ensuring the taste and quality of food. Climate change, together with human-directed causes (Section 2) may result in a loss of pollinator ranges and pollination timing. These changes represent a serious threat to the future of food production.
Pollinators are a diverse group of species, over 200 000 worldwide, many of them wild pollinators and only a small subset managed domestically (e.g., honey bees). Global agriculture relies heavily on pollination and this dependence has increased more than three-fold since the 1960s with wild pollinators playing a far greater role than those that are managed.4 According to a recent IPBES review, the worldwide economic benefit from pollinators in commercial agriculture is estimated to be over €550 billion per annum.5
Lefleve Xavier (2014); Marshall et al. (2015).
Inouye et al. 2016; see note summaries in Appendix 1. IPBES 2016.
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FAO-IPCC Expert meeting on climate change, land use and food security