23.03.2020 |

Water plays a key role in climate change adaptation and mitigation, UN

Agricultural water management plays a key role (Photo: CC0)

Climate change will affect the availability, quality and quantity of water for basic human needs, undermining the enjoyment of the human rights to water and sanitation for billions of people, says a new UN report. The alteration of the water cycle will also pose risks for energy production, food security, human health, economic development and poverty reduction, thus seriously jeopardizing the achievement of the Sustainable Development Goals (SDGs). This is the message of the UN World Water Development Report, published by UNESCO on behalf of UN-Water ahead of World Water Day, which was celebrated on March 22. The authors call on states to make more concrete commitments to address the challenge. According to SDG 6, access to safe drinking water and sanitation must be guaranteed for all by 2030. However, this will be difficult to achieve since 2.2 billion people currently do not have access to safely managed drinking water, and 4.2 billion or 55% of the world population are without safely managed sanitation.

According to the report, water use has increased six-fold over the past 100 years and will continue to grow at a rate of about 1% per year as a result of population growth, economic development and shifting consumption patterns. Climate change, along with the increasing frequency and intensity of extreme events such as storms, floods and droughts, will affect the availability and distribution of water resources. This will aggravate the situation in countries which are already experiencing ‘water stress’ and generate problems in regions where water is still abundant. Changes in water supply will not only hit agriculture but also industry, energy production and fisheries. Water quality will also be affected by increased water temperatures and a decrease in dissolved oxygen, leading to a reduction in the self-purification capacity of freshwater basins, the authors warn. “We will see increased risks of water pollution and pathogen contamination caused by floods or higher concentrations of pollutants during periods of drought. In addition to the impact on food production, the effects on physical and mental health – linked to disease, injury, financial loss and the displacement of people – are therefore likely to be considerable,” they write. Many ecosystems, particularly forests and wetlands, are also under threat. The degradation of ecosystems will not only lead to biodiversity loss, but also affect the provision of water-related ecosystem services.

The report includes a chapter on food and agriculture which highlights where land-water linkages are expected to become apparent in terms of climate impacts and where practical approaches to land and water management offer scope for both climate adaptation and mitigation through agriculture. Agriculture, which accounts for 69% of freshwater withdrawals, still dominates global water use, but competition from other sectors is slowing the growth of freshwater allocations to the agriculture sector. Expansion and intensification of crop production on irrigated land is the most significant driver of agricultural water demand. According to the authors, the specific challenges for agricultural water management are twofold. The first is the need to adapt existing modes of production to deal with higher incidences of water scarcity and water excess. The second is to ‘decarbonize’ agriculture through mitigation measures that reduce greenhouse gas emissions and enhance water availability.

With respect to adaptation, the authors propose approaches to land and water management, soil conservation and agronomic practice that sequester carbon and reduce greenhouse gas emissions. These measures are summarized under the umbrella of Climate-Smart Agriculture (CSA), a concept which has also earned criticism from NGOs. The report claims that CSA practices help to retain soil structure, organic matter and moisture under drier conditions, and include agronomic techniques (including irrigation and drainage) to adjust or extend cropping calendars to adapt to seasonal and interannual climate shifts. The authors point out that the role of agricultural water management is central to agriculture’s adaptive response. In rainfed agriculture, adaptation is determined largely by the ability of crop varieties to cope with shifts in temperature, as well as by soil moisture management which is crucial in maintaining soil structure and promoting root growth and plant establishment to sequester carbon. Irrigation would allow cropping calendars to be rescheduled and intensified, thus providing a key adaptation mechanism for land that previously relied solely on precipitation.

In terms of mitigation, the authors mention two paths for reducing emissions: carbon sequestration through organic matter accumulation above and below the ground, and emission reduction through land and water management, including adoption of renewable energy inputs. Increased use of renewable energy in agriculture, such as solar pumping, provides additional opportunities to cut emissions and to support the livelihoods of smallholders, the authors argue. They propose specific agroforestry and agronomic practices targeted at carbon sequestration and emission reduction. One of them is agroforestry, which exists in multiple forms, from productive trees for fruit products to native trees for wind breaks and shade. “Agroforestry can have positive impacts on soil water infiltration, soil water storage, groundwater recharge, runoff and erosion control, soil nutrient cycling, and biodiversity,” the authors highlight. In addition, alternate wet-dry cultivation of rice has been shown to reduce methane emissions, maintain yields and reduce water demand by up to 24% when compared with continuous flooding. In forestry, the best options for mitigation are reducing emissions from deforestation and forest degradation and afforestation to sequester carbon. (ab)

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