In this context, legislation to protect the environment is taken to mean that affecting water, soil and air and excludes wildlife, habitats and bio–diversity. In practice, of course, resource protection impacts on wildlife, habitats and bio–diversity as well as on human health.
Agriculture is responsible for over 70% of nitrates and over 40% of phosphates in English waters (Defra, 2002). Elevated levels of these nutrients can contribute to eutrophication of marine and freshwater and cause ecological harm. Agriculture is also responsible for around 80% of UK ammonia emissions to air, although the contribution from pig farming is about 9% (Defra 2002). This contributes to acid rain that can damage forests, lakes and rivers; and it adds nitrogen to nutrient–poor soils (e.g. heathland) that can change the type of vegetation. And each year there are many complaints to local authorities about odours from agricultural premises (Defra 2002).
There are a number of pieces of legislation that affect or will affect pig production that seek to avoid, limit or minimise emissions to the environment: these include the Nitrates Directive, Integrated Pollution Prevention and Control (IPPC) Directive (larger pig units), Water Framework Directive, Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) Regulations 1991, Animal By–products Regulation, and the proposed Waste from Mines and Quarries and Agricultural Premises (England and Wales) Regulations that will implement the Waste Framework Directive for agriculture.