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Auctions, nature-based solutions and offsetting in the Hampshire Avon

A post by Ruth BardenDirector of Catchments & Environment

The Chalk Streams of the Hampshire Avon catchment are world renowned for their beauty and the unique wildlife. Unsurprisingly, these watercourses are designated as a Special Area of Conservation.

However, there is a conflict here. The need for housing development places pressure on the natural environment, hence requiring a balancing act between economic growth and the associated services such as waste treatment and disposal, and environmental conservation. Wessex Water and Wiltshire Council have been working with EnTrade to help address this balance with respect to increasing phosphorus loads from further housing development.

A Chalk Steam in the Hampshire Avon catchment (Credit: Tom Aspin)

Phosphorus is an essential nutrient for cellular growth in all living things – plant, animal and human. Humans only need a certain amount of it – what we don’t need is excreted. Similarly, plants and crops only absorb from the soils the amount needed for growth, so fertiliser additions in excess of this are wasted. As a result, excess phosphorus ends up in our watercourse, both via sewage treatment works and runoff from farmland. This creates excessive algal and weed growth in our chalk streams.

Therefore, in order to enable development growth in this catchment all new houses need to be phosphorus neutral. Wessex Water is voluntarily reducing phosphorus loads discharged from our assets to help improve the environment – over and above existing regulatory requirements – but we are also looking to the agricultural sector to help offset the phosphorus which will be generated.

With this in mind, in June an EnTrade auction working with the Pewsey Vale farmer cluster was held, convened with the help of Simon Smart (Black Sheep Consultancy) and Paula Sage (MOD Estates). Farmers put forward a range of options to reduce phosphorus loads, including wetland creation, woodland planting, cover crops, buffer strips and a whole load more!

Although the requirements of Wessex Water and Wiltshire Council are slightly different (in terms of the longevity of the phosphorus reduction measure), plenty of viable proposals were suggested. Both parties are now liaising with specific farmers to purchase the offsets available.

Wessex Water is looking for shorter term measures with a duration of up to 5 years, and we are also interested in obtaining further data about the catchment. Therefore, we are contracting with farmers to:

• Plant cover crops and buffer strips – further enhanced with nectar seed mixes to improve biodiversity as well as providing phosphorus reduction
• Deliver areas of wildflower planting
• Purchase direct drilling equipment in order to switch to minimum till methods, reducing phosphorus leaching
• Collect data that will support further understanding of the catchment via soil testing, weather stations and wider phosphorus analysis.

In total, this will provide a phosphorus reduction of 130kg over four years, in addition to 3.15ha improved for biodiversity and 80tCO2eq/y of carbon sequestered. The additional data will help to improve our models and understanding of weather, soil and localised water quality data and to demonstrate improvements.

Similarly, Wiltshire Council is reviewing applicable measures with a view of contracting with farmers for wetland and woodland options, also providing additional carbon and biodiversity benefits.

What started off as a simple multi-buyer phosphorus offsetting auction will now deliver wider environmental benefits, which may be tradable in the future as credits, and a way forward for local authorities and water companies to deliver nutrient reductions in sensitive environments. In addition, the farming sector has the opportunity to increase their business diversity, providing different services rather than products, to a range of buyers over a longer time period (typically decades), thereby supplementing income streams and giving certainty in uncertain times. So, it really is a win for all!

The auction links back to the Hampshire Avon Marketplace challenge.