Climate change and increase in drought and flooding
Climate change is set to bring on a change in our weather systems, with extreme weather conditions becoming more frequent.
This is likely to include more intense and frequent flooding due to an increase in periods of heavy or intense rainfall. Simultaneously, climate change predictions anticipate an increase in drought events during summer months due to longer periods of extreme heat and lack of rainfall. This is expected to increase extreme floods from a one event every 20 years to one event every 3 years in the near future (2021-2040) .
To reduce the impact of these extreme weather events on agricultural production, land managers should target measures to increase water infiltration and retention. This can be achieved through a series of nature-based solutions implementing land management practises which work with the land to help prevent disruption from these changing weather events.
 Kirkpatrick Baird, F., Stubbs Partridge, J. & Spray, D. 2021. Anticipating and mitigating projected climate-driven increases in extreme drought in Scotland, 2021-2040. NatureScot Research Report No. 1228.
Water retention in soil (Soil type and organic matter)
The key component in both drought and flood prevention is ensuring rain can penetrate the surface, infiltrate to deeper levels and be retained. In doing this, soil can endure heavy rain events through up taking water more quickly and storing it, thus reducing flood risk. Increasing the water retention capacity of the soil also enhances resilience to drought. This level of infiltration is in part determined by the soil type. Sandy soils, which have relatively large particles, have a greater infiltration rate when compared to clay soils which comprise finer particles.
However, the level of water retained in the soil is largely driven by the amount of organic matter present. Organic matter refers to carbon containing compounds within the soil, which can include fresh plant residue (such as litter and decaying roots) and small living organisms, as well as decomposing crop residue and manures. The organic matter itself acts like a sponge soaking up and holding onto water as it infiltrates through the soil.
Organic matter can help fill large pores in sandy soils helping them retain water and can loosen up particles in clay soils allowing water to flow to deeper levels.
Increasing soil organic matter (manures, fertilisers, cover crops)
As organic matter can help retain water in soils, increasing the amount of organic matter within a soil can help greatly in combating drought and drainage.
A method of increasing the organic matter within soils can be the spread of manures / organic fertilisers. Bulky manures and organic fertilisers applied in frequent and heavy application can bring on quick changes to the level of organic matter in the soil. Alternatively, cover crops can be sown. Cover crops increase organic matter through protecting the soil from erosion, adding organic content to the soil through roots and foliage, and creating habitat for microorganisms.
To further improve soil health, fertility and enhance both infiltration and water retention, cover crops can be retained through the growing season before being ploughed in as a green manure the following autumn or spring. While this sacrifices a field for the growing season, green manures act as a break crop, helping to suppress weeds and build soil fertility. This reduces the requirement for inorganic nitrogen and benefits last for several years. Dense and deep-rooted cover crop species (e.g. Phacelia, Mustard, Rye, Oats) break up the soil increasing soil drainage, reducing run-off, while including legumes (e.g. crimson clover and vetch) enhances nitrogen fixation. Many of these species produce an abundance of flowers, benefiting pollinators and natural enemies such as parasitic wasps. Alternatively, reduced or no-till have been found to greatly increase the amount of organic carbon in soil. Additionally conventional tillage may increase compaction of soil below the tillage depth, resulting in an increase in water and wind erosion to topsoil. A reduction in tillage can allow for soil organic matter to accumulate in soils and reduce compaction.
Multi-species swards are, as they sound, swards made up of multiple plant species. This method of sward establishment can provide multiple benefits both agriculturally and environmentally.
Different plant species have different tolerances to different water levels, meaning the sward as a whole can cope with a wider range of water levels. In times of drought, deeper rooting plant species (e.g. chicory) can access water deeper in the soil making them more resistance to low water levels allowing them to thrive within the sward. Whereas in a monoculture, once the water table hits a certain level, all plants may fail.
Simultaneously, while providing resistance to drought, multi-species swards also increase water infiltration and uptake decreasing the likelihood of flooding. This is because the roots of multispecies swards differ in length, allowing water to trickle down to lower levels and reducing compaction, which increases filtration and drainage from the surface.
Additionally, multispecies swards provide a wider range of habitats and food sources to a more diverse number of animals and fungi.
Targeted tree planting to hold water
The utilisation of trees to enhance farming is nothing new, however recently it has gained some popularity under the name ‘agroforestry’. Trees can help greatly in the prevention of floods, this is because of their extensive root structure breaking up soil and increasing its infiltrability, as well as canopy and branches slowing down the rate at which water reaches the ground. Additionally, their presence slows down the overland flow of water reducing the likelihood of flood occurrences. Furthermore, trees add organic matter to the soil. This addition of organic matter boosts water retention as stated above, providing benefits in the reduction of drought and floods.
Trees not only sequester and store carbon, but also help to mitigate the impact of climate change. They provide livestock with shade and shelter, reducing heat stress and exposure with positive implications to welfare and production.
Sustainable water use
Improving the efficiency in which we use our fresh water is likely to become ever more important in a changing climate. Harvesting rainwater can provide a method to sustainably gather water during wetter periods, which can then be utilised during drier spells. These rainwater harvesters can be installed to catch rainwater that drains from sheds and infrastructure and is stored on site in tanks. Alternative Watering systems for field grazed livestock also offer an opportunity to supply drinking water for livestock in remote areas subject to water quality. These can consist of abstraction or pumping systems that meet site and stock drinking requirements.
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