The theme of World Soil Day 2020 is ‘Keep Soil Alive, Protect Soil Biodiversity’; with the aim of raising awareness, discussing challenges in soil management and tackling soil biodiversity loss. So why is this important to us as individuals, organisations and communities, and how does soil come in to the project work being completed by RammSanderson on a day to day basis, across all of our departments?
The importance of healthy soil
There is a complex community beneath our feet comprising burrowing animals, insects, fungus, bacteria and much more that are co-dependant on the plants and activity at the surface. Plants and animals at the surface nurture and protect the creatures beneath the surface that in return feed and protect our plants. This cyclical process keeps soils healthy and fertile and taken together form soil biodiversity.
Impacts and threats to soils
Agricultural practice and construction methods significantly impact soil biodiversity but it is not just what we plant or treat the land with that affects our soils and simple changes could have significant benefits. Recent advances in agricultural policy and practice and the adoption of biodiversity net gain have the potential to greatly improve our soil biodiversity. Incentives for famers to manage land for ecology, biodiversity and natural flood risk management are leading to a whole range of beneficial measures such as wide field margins packed with wildflowers and grasses which in return provide valuable resources for pollinating insects, butterflies, birds, mammals and more.
Changes to how we manage our hedgerows, reducing or cycling the flailing process allows overwintering invertebrate populations to thrive. This not only has benefit for biodiversity but for the productivity of the land. Furthermore, widening the field margins is showing significant benefits for mature standard trees within hedgerows. This year we have seen first-hand the benefits to mature oak trees within field margins in less than 2 years after reducing impacts from ploughing, by moving the ploughed edge away from the boundary just a few metres. Creating ponds, ditches and wetland areas for flood storage have significant ecological benefits whilst often reducing flood risk downstream.
Protecting soils through providing vegetation cover during times of year with the highest rainfall will help reduce soil erosion, which in turn reduces pollution to watercourses. Winter crops, ‘green manures’ and leaving fields fallow in farming contexts, allowing pasture and hay fields to recover from heavy grazing or cutting in autumn and growing taller in time for winter also will help protect soils. For construction sites similarly site managers should ask themselves if they need to clear all vegetation from all areas of a site as part of site establishment? If more areas were left vegetated for longer, soils would be protected and would therefore recover more quickly post completion.
How do RammSanderson consider soils?
As part of our work on Biodiversity Net Gain, it is important to accurately account for the impacts on soils within our calculations. If an area is temporarily cleared during construction or utilised for storage etc. and to be reinstated as habitat following construction, it is important to factor in sufficient time for soils to recover from compaction, pollution, removal/replacement and erosion within our calculations. Therefore whilst an area may be cleared for a compound for example for 3 years, it may take another 3 years or longer after reinstatement for the conditions to return to their pre-development condition; let alone to begin to show signs of any enhancement. It may therefore be appropriate for alternative areas either on site or off site to provide the required enhancement to create a demonstrable net gain.
Soil types and conditions are also considered when assessing habitat types in the field. Different habitats exist under different conditions and therefore when considering habitats, the species present can often be indicative of the specific soil conditions present locally. It may then be necessary to consider how these conditions can be protected to ensure the longevity of a habitat and species.
Similarly, land use and ground conditions play a big role in determining flood risk. Even under natural conditions soil and rock type can influence what happens to rainwater. Impermeable soils and ground conditions will not allow water to infiltrate, leading to runoff and potentially increasing flood risk. Permeable soils and ground conditions on the other hand will allow infiltration. As such when considering flood risk and drainage it is important to fully understand the history of a site and its ground conditions. Runoff assessments look at the classification of soils and ability to allow infiltration. This is likely to be confirmed further by onsite testing prior to construction.
Natural Flood Risk management can provide significant benefits but whilst this would perhaps provide the greatest benefit adopted across a strategic level, benefits and gains can successfully be achieved by following these principals on a site specific scale and will help in achieving biodiversity and carbon offsetting goals and improvement to soil biodiversity, by holding water in the landscape for longer. Planting of trees and hedgerows for example can impede runoff/increase interception. This leads to a reduction in peak flows of watercourses. In areas of historical soil compaction the reintroduction of vegetation can have huge benefit as the roots will break up the soil and introduction of new organic matter will improve soil composition and structure. Soil compaction is likely to lead to runoff however introduction of vegetation not only allow interception but overtime is likely to promote infiltration.