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Addressing nitrogen waste is essential for restoring biodiversity

Guest blog written by Emily Hunter, Woodland Trust


With the recent budget announcement, Conservative leadership contest and the COP29 for climate, you’d be forgiven if COP16 in Cali, Colombia, passed you by. Over two weeks, parties to the International Convention on Biodiversity met to discuss how Governments will deliver on commitments made in 2022 as part of the Kunming-Montreal Global Biodiversity Framework (GBF). Yet, despite the fact that the world is facing a global biodiversity crisis, COP16 got barely a mention in UK media.


Discussions at this year’s COP focussed on delivering the commitment to protect 30% of land and sea by 2030, and financing nature’s recovery, including an agreement for companies that make use of Digital Sequence Information to pay into a new fund. However, one area that doesn’t appear to have garnered much attention, is Target 7 of the GBF.


Target 7 of the Kunming-Montreal Agreement commits governments to reducing the negative impact of pollution by 2030, including “by reducing excess nutrients lost to the environment by at least half, including through more efficient nutrient cycling and use”. One of the biggest sources of nutrient pollution is nitrogen.


Nitrogen is essential for life on Earth and, in its inert form, makes up 78% of our atmosphere. However, human activity has put the natural nitrogen cycle out of balance and reactive nitrogen is wreaking havoc on our sensitive ecosystems. It is also a potent greenhouse gas and harms human health by contributing to air pollution.


Agriculture is a major source of nitrogen pollution, and of ammonia in particular. Ammonia from livestock farming is lost to the atmosphere, while excess nitrogen in soils pollutes watercourses through leaching or runoff. A UK Nitrogen Balance Sheet, commissioned by the Sustainable Nitrogen Alliance, shows significant amounts of nitrogen waste from UK agriculture, with large amounts wasted and lost to the air and water. On average, only around 50% of nitrogen applied to soils is actually taken up by crops. It’s clear improving nitrogen use efficiency in agriculture is not only essential for meeting our global target to halve nutrient losses, but would also make financial sense for farmers.


Photo by: Ben Lee/WTML


Many of our native habitats have evolved at low nutrient levels, so reducing nitrogen pollution is essential for restoring biodiversity. Ancient woodland is one of our rarest habitats, covering just 2.5% of the UK. Many species characteristic of ancient woodland are nitrogen-sensitive, meaning they start to suffer or die-off at high levels of nitrogen. Yet the vast majority of the UK’s native woodlands exceed the critical load for nitrogen deposition, at which we begin to see deterioration. High levels of nitrogen lead to a decline in some species and encourage nitrogen-tolerant species. Over time, this alters the whole ecology of the woodland, with rarer, specialist species declining. The effect is similar for other sensitive habitats such as wildflower meadows, with over two thirds of our native wildflowers requiring low or medium levels of nitrogen. There is also emerging evidence that high levels of nitrogen could be contributing to oak decline.


Despite the clear importance of reducing nitrogen pollution for nature’s recovery, research shows we are massively off track. A report by the Sustainable Nitrogen Alliance, using analysis from IEEP UK and Aether, found that the UK is unlikely to meet the GBF target to halve nutrient waste. What’s more, the UK Government is yet to even set indicators to enable us to measure progress on meeting the target, while international governments failed to sign-off on a monitoring framework for the GBF in Cali last week.


The report highlighted that existing policies and legislation are fragmented, tending to focus on only one source of nitrogen pollution and therefore risking pollution swapping, where actions to reduce one form of nitrogen inadvertently increase another source. The authors identified an alternative approach that would have more chance of delivering UK targets on nitrogen and air quality by adopting a system-wide approach. This scenario would place an emphasis on both reducing nitrogen losses and requiring greater reductions in the input of nitrogen, through increased nitrogen use efficiency and shifting demand away from nitrogen intensive commodities. However, for this to be successful, we would need to see an end to siloed working and ideally development of a National Nitrogen Strategy requiring a cross-departmental, integrated approach to reducing nitrogen waste.


The Sustainable Nitrogen Alliance continues to advocate for an approach that tackles all sources of nitrogen overuse and waste to benefit health, climate and nature. The importance of reducing nitrogen for nature’s recovery is too important for it to be left on the side-lines.


Cwm Mynach, Woodland Trust. Photo by: Mark Zytynski/WTML




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