Eutrophication in a river, (c) Copyright N Chadwick and licensed for reuse under this Creative Commons Licence
Today's blog is written by Nik Perepelov, RSPB's Senior Water Policy Officer, detailing the importance of nutrient neutrality in preventing our ecosystems being further choked by excess nutrients.
It’s no secret that our rivers, lakes and estuaries are not in a good way. Government’s own data show that just 14% of them are up to scratch ecologically. Raw sewage spills get all the publicity, but even these account for just 1-in-20 of known reasons for failure. Much more widespread, and harmful, is the impact of excess nutrients, primarily nitrogen (N) and phosphorus (P). These are much harder to detect with the naked eye, but if you’ve ever seen a stagnant waterway choking in brown algae, you’re familiar with their effects.
I thought nutrients were a good thing?
Generally yes, most living things depend on N and P to make the fundamental building blocks of life such as DNA and proteins. However, too much of these nutrients creates a banquet for other organisms, like algae. These organisms deplete oxygen levels and crowd out sunlight, threatening the aquatic ecosystem they have bloomed in.
Where are these excess nutrients coming from?
Broadly speaking, most excess nutrients come from us. Excess nutrients come from inputs to our food, in the form of fertilisers, or outputs from our food, in the form of excrement and urine. In addition to these, livestock farming directly generates excess nutrients in the form of manure; wastewater can contain excess P from detergents and even toothpaste. Where nutrients are an issue, agriculture is the largest single source for both nitrogen and phosphorus, with sewage a significant no.2, particularly for P.
Cattle grazing (c) rspb-images
What impacts are we seeing?
Excess P is the leading cause of waterbody failure, particularly inland. Coastal and estuarine waters are particularly sensitive to excess N. Algal mats are blooming across the country, smothering the surrounding ecosystem and destroying aquatic and intertidal habitats. Scandalously, this includes large parts of our nationally and internationally important protected site network, that is, our most valuable, rare and precious habitats. Protected sites, as the name suggest, are meant to benefit from safeguards to maintain their special features. Across England, however, the scourge of nutrients has pushed a growing number of internationally important lakes, rivers and coasts to the brink.
How has this impacted housing?
Natural England are tasked with ensuring sites are afforded their statutory protections. Their tools here are limited – for example, most agricultural practice goes effectively unchecked – but planning is one domain where protections are firmly enshrined. After decades of accumulated nutrient pollution, Natural England have concluded that at least 27 protected sites – from Cumbria, to Devon and Norfolk to Shropshire – are on the edge and cannot continue to take excess nutrients without further choking their protected habitats and species. Any new housing in those areas, therefore, has to mitigate the impact that those new toilet users would have, by reducing inputs elsewhere in the catchment. A development that offsets the same volume of nutrients that it inputs is said to have demonstrated “Nutrient Neutrality” and can go on to get built. Some of these offsets, like wetlands and bufferstrips on farms, can be great for nature, as well as helping improve water quality.
Housing estate under construction, (c) rspb-images
Where have things got to with Nutrient Neutrality?
Natural England advice on Nutrient Neutrality applied to 74 local planning authorities and initially led to delays in planning permission for some 100,000 new homes. This backlog is being cleared thanks to raft of initiatives, many of them seizing the opportunity to design Nature-based Solutions and innovative markets in ecosystem services. Mitigation has been slower to come online than some housebuilders would like, and Government has been throwing significant money and new legislation at the issue. We’re keen that these initiatives are given the full opportunity to bear fruit, so strongly oppose suggestions that these last-line-of-defence protections should be dropped.
Healthy waterways are perfectly capable of handling some volume of nutrients (ideally less over time as we upgrade sewage infrastructure and manage land more sensitively). Accumulated harm over the years, bypassing or poorly implementing protections the sites are meant to benefit from, has chipped away this capacity for nature to help us out in safely removing our toilet waste. These sites are now on the edge of the ecological abyss and, if we take seriously our commitments not to turn every river into an open sewer, enough is enough. Instead of dipping ever deeper into the environmental overdraft and just paying the associated charge, we need to build up significant savings by getting these sites into recovery. Building this headroom involves addressing both agricultural and wastewater sources of nutrients and thereby enabling both sustainable development and flourishing natural places.
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