12. Natural Resources and Environmental Impacts of Food Systems- Land and Water.pdf

Natural Resources and Environmental Impacts of Food Systems: Land & Water Romy Chammas MSc. 2024  Introduction As seen in Table 1, the actual use of most natural resources in the food system...

Natural Resources and Environmental Impacts of Food Systems: Land & Water Romy Chammas MSc. 2024  Introduction As seen in Table 1, the actual use of most natural resources in the food system activities is concentrated in the primary step: food production stage. The main exceptions are fossil fuels and minerals. Currently, 70% of fossil fuel use is for off-farm activities, that is the next steps of the food system activities (post-food production). Land, Soils, and Landscape  Land Use and Food Systems People have increasingly transformed land and ecosystems in order to increase food production, leading to major changes in biodiversity, biogeochemistry, and climate. (Ellis et al., 2013) Total global land area = 149 million km2 15 million km2 are predominantly used for crop production. 34 million km2 are predominantly used for rangelands (grassland and other areas of native vegetation for grazing livestock or wild animals). Globally, croplands produce the largest share of food, although the contribution from other sources (fisheries, hunting, rangelands) should not be underestimated. Within the food system, land is predominantly used for primary production, although large areas are allocated to other activities like food processing, retail, and restaurants.  Land Use and Food Systems Soils are a major component of the land resource. Important determinants of the suitability of land for agriculture: Soil quality Slope Climate  Land Potential Not all land on earth has the potential to sustainably support agricultural production. For a particular piece of land, this ‘land potential’ is a function of both the land’s current production potential and the land’s resistance and resilience to degradation. (UNEP, 2016)  Land Potential FAO distinguishes 3 classes of cropland potential: ✓ Prime ✓ Good ✓ Marginal/unsuitable Globally, 28% of the cultivated land is classified as prime quality, and 53% as good. The productivity of inputs such as labor, seeds, water, and nutrients is higher on prime land than on good or marginal land. The potential of a specific piece of land is not static. Land potential can be increased through innovation and investments. It can also decline through soil loss and other forms of degradation.  Land Potential The land quality of a certain plot or region can be improved by good management, but can also deteriorate in the case of poor management. Much of the current prime agricultural land has been improved over time. Soil acidity has been corrected by liming. Soil fertility has been increased through fertilization and use of organic materials. These are generally short-term changes that need to be maintained over time.  Land Potential More long-term and dramatic changes to land potential have been achieved through: Modifying water flows through the soil via terracing Installing surface and sub-surface drainage systems Terraced fields decrease both erosion and surface runoff, and are often used to support growing crops that require irrigation. Terrace abandonment often occurs when labor costs rise, reducing the profitability of managing steep lands for agriculture. This could lead to increased soil erosion.  Efficient and Sustainable Use of Land Higher crop yields could lead to higher labor productivity and better socio-economic outcomes. Higher crop yields could reduce the need for additional agricultural land and thus slow down the rate of deforestation. On a local scale, more efficient agriculture is likely to be more profitable and could therefore lead to an expansion of the cultivated area. On a global scale, higher crop yields likely lead to lower commodity prices, and thus stimulate the demand for products like meat and biofuels (in turn increasing the demand for crops).  Unsustainable Use of Land Soil and land degradation are taking place in many areas. Soil degradation is the decline in the fertility or future productive capacity of soil, largely due to improper use or poor management. Soil degradation is generally caused by: Soil erosion: by wind or water Chemical factors: nutrient depletion, toxicity due to acidity or alkalinity, excessive use of fertilizers Physical degradation: soil compaction Biological factors: affect the microbial activity of the soil Globally, 33% of earth’s land surface is affected by some type of soil degradation.  Unsustainable Use of Land Land and soil restoration can improve their quality and productivity. Over the past decades, restoration projects have been successfully carried out. For example: Windbreaks, which are usually one or more rows of trees or shrubs planted in a manner that provides shelter from the wind, protect soil from erosion.  Consequences of Unsustainable or Inefficient Land Use Unless current agricultural land is used more efficiently, population growth and an increased demand for food, animal feed, and biofuels are likely to lead to cropland expansion. This will result in the additional conversion of natural vegetation (forests and rangelands) and subsequent loss of biodiversity and ecosystem services. Land degradation could worsen this problem, as it typically leads to lower crop yields, and consequently to a demand for more new lands. Land degradation also leads to a lower efficiency of other inputs.  Consequences of Unsustainable or Inefficient Land Use Land degradation also affects livelihoods. Many people are facing a downward spiral of land degradation, falling yields, and the lack of means to invest in land quality improvements. (Tittonell & Giller, 2013) Over 40% of the very poor live in degraded areas. (Conway, 2012) Moreover, unsustainable land management has large implications for future crop yields and related food production, as following generations will also crucially depend on productive land. Therefore, the sustainability of land use should be assessed at a timescale of hundreds (or even thousands) of years.  Future Land Use In order to meet the growing global food and feed demand, the total cropland area is still growing. At the global level, yield increases are highly contributing to the growth in crop production, but cropland expansion is also significant in increasing crop production. This expansion is often at the expense of natural areas such as forests, wetlands, and rangelands. Other factors that will increase the demand for additional cropland area include the growing demand for biofuel and bio- energy as well as soil degradation. Water  Water and Food Systems Fresh, clean water is essential for humans, crop and livestock production, and land-based aquaculture. In the rest of the food system, water is also needed for activities such as food processing, preparation, and waste disposal. Vast amounts of water are needed for food production. It is estimated that the daily average per capita water use for food production is nearly 4,000 liters. (Hoekstra & Mekonnen, 2012) Rain-fed agriculture depends on ‘green’ water, whereas irrigated agricultural depends on a combination of ‘green’ and ‘blue’ water. Irrigated agriculture currently accounts for approximately 70% of the total global ‘blue’ water withdrawals. (OECD, 2010)  Water and Food Systems In many areas, water is the main limiting factor to increase crop production. A good and reliable supply of water to the plant (either by rainwater or through irrigation) is thus key in improving the overall resource efficiency of agriculture.  Water and Food Systems Water as a natural resource has a number of important characteristics that make it different from other natural resources: ✓ Water is not actually used/exploited, but rather evaporates and becomes part of the larger water cycle. ✓ The availability of water is highly localized. An excess of water in one region cannot easily be transported to regions with water shortages. Around 1/3 of the global population currently lives in countries suffering from medium to high water stress. ✓ The presence of sufficient water for crop growth is uncertain, as the quantity and timing of rainfall is uncertain. ✓ Water is, in principle, a renewable resource. However, in certain regions, water is being used from aquifers that contain ‘old’ water which could be hundreds of years old. This will finally lead to depletion of these aquifers, labeling water in this case as a non-renewable resource.  Water and Food Systems Globally, there are large regions of irrigated agriculture where crop production is under stress due to irrigation water shortages (Figure 21). The irrigated global area has doubled over the last 50 years, leading to a rapid growth in crop production but stronger dependence on larger amounts of water. In order to improve a reliable supply of surface water for irrigation, dams have been constructed in many rivers, and local reservoirs have been built for the temporary storage of water. In some regions, the use of groundwater sources for irrigation has intensified, largely driven by subsidies on electricity or diesel for pumping.  Unsustainable Use of Water As with other resources, both an efficient and sustainable use of water is important. An efficient use of water refers to the ratio of the volume of water arriving at plant level and the final useful product (crop yield). It could also refer to the ratio of water arriving at plant level and the amount of extracted water (Aquifers). A sustainable use of water refers in the case of groundwater wells to a situation of no depletion of aquifers, or in the case of surface waters to no large-scale pollution or disturbance of watersheds.  Unsustainable Use of Water The current levels of water use for irrigation are unsustainable in many cases. The current use of surface water has various negative environmental impacts, both on aquatic and terrestrial ecosystems. Farmers as well as regional and national authorities have carried out many interventions to enhance water availability. These include damming of rivers, changing flow regimes, and the draining of wetlands. Even though many interventions are quite small, their cumulative effect on a river basin can be substantial, often with large consequences for biodiversity, the local climate, and people living downstream.  Unsustainable Use of Water In addition to surface water, groundwater is another source of water for irrigation. Water is sometimes pumped from layers that are located very deep below the surface. Some of these water reserves have existed for hundreds of years. At least 20% of the world’s groundwater aquifers are considered to be overexploited. (Gleeson et al., 2012) Especially in Asia (Upper Ganges) and North America (California) This leads to a lowering of groundwater tables, resulting in increased pumping costs and lower availability of irrigation and drinking water.  Case Study: Rapid Growth of Groundwater Irrigation in India Groundwater is a critical resource in India, accounting for over 60% of irrigation water and 85% of drinking water supplies. Due to various factors (including energy subsidies and the availability of small pumping equipment), many farmers opted for groundwater irrigation. As a result, groundwater is now the predominant source of water supply for irrigation in India. The pressure on groundwater resources for irrigation has continued to grow over the past 40 years. The Upper Ganges aquifer in North-West India and Pakistan now has the largest groundwater footprint, meaning that more groundwater is being used than replenished. (Gleeson et al., 2012)  Water-Use Efficiency The water-use efficiency can be defined in several ways. The more narrow definition, widely used in irrigation, is the ratio of water arriving at plant level and the amount of extracted water. The broader definition also assesses the water productivity: How much crop (or value) is being produced per volume of water applied. Water productivity is closely related to the efficiency of other resources such as the quality of land and management practices.  Water-Use Efficiency In many regions, the water-use efficiency is currently low. Losses of 50% of water are common. In many countries, inefficient techniques are still being used, such as flooding or high pressure rain gun technologies, which use considerably greater quantities of water than low pressure sprinklers and drip irrigation techniques. (OECD, 2008) In irrigated agriculture, water losses can occur before the water has even reached the crop roots. For example: Leakage in channels, direct evaporation during irrigation, or runoff and percolation losses caused by over-irrigation.  Water-Use Efficiency In terms of the broader definition (water productivity), large inefficiencies occur, for example due to pests, low soil fertility, unsuitable varieties, or wrong timing of irrigation. A comprehensive global overview of current water efficiency in agriculture and along the food chain is, however, lacking.  Consequences of Inefficient or Unsustainable Water Use Inefficient water use can have several negative consequences: More rapid depletion of non-renewable water resources Lower crop yields than potentially possible Lower water availability for farmers, other users, and downstream ecosystems Unsustainable water use will cause depletion of aquifers, which will mean that future generations cannot profit from this source.  Future Water Use Agricultural water use is projected to slightly diminish in spite of increased production. (OECD, 2012) In certain regions, however, climate change will lead to lower or more unpredictable rainfall, thus increasing the need for irrigation. On the other hand, water use in other sectors, such as manufacturing and private household use, is projected to increase sharply due to population growth, increasing prosperity, and urbanization. By 2050, an expected 40% of the world’s population will be living in severely water-stressed river basins. (OECD, 2012)  Future Water Use Climate change is expected to have a large effect on the availability of water in many regions by affecting precipitation, runoff, water quality, water temperature, and groundwater recharge. (HLPE, 2015) Due to reduced precipitation or increased evapotranspiration, droughts may intensify in some seasons and areas. Without mitigation measures, this might lead to reduced crop productivity in certain regions. (IPCC, 2014b) Climate change will also lead to sea level rise, which may lead to flooding of fertile coastal regions, as well as to salinization of freshwater resources in coastal areas.