Today’s blog has been written by Rob Field, RSPB Senior Conservation Scientist, discussing his new paper which quantifies the importance of looking after habitats for climate change, as well as nature
This year was to have been a crunch point for international efforts to stem the loss of biodiversity and restrict climate change to below 2°C of warming. We should have seen thousands of delegates gather at the Conference of Parties of the Convention on Biological Diversity and the UN Framework Convention on Climate Change.
However, COVID-19 intervened in a dramatic, far-reaching and for many, devastating, way. Further evidence, as if it were needed, not only of the effect that people have on the environment, but also how those effects can rebound on us. There is now much talk of a so-called green recovery, building resilient economies on low carbon and sustainable foundations.
One such foundation should be working in tandem with nature to help reduce the effects and impacts of climate warming – a ‘nature-based solution’ to climate change. Nature-based Solutions has become a real buzz word in the biodiversity and climate policy arena in 2020. This is the idea that, while many of human societies’ problems (flooding, climate warming, drought and desertification) are caused by disruption to natural systems, the solutions can also be found in natural systems and processes.
RSPB Wallasea Island is an example of a large scale project to help combat climate change and coastal flooding © David Wootton (rspb-images.com)
Identifying key areas for carbon
Accordingly, RSPB scientists, working with the University of Aberdeen, have recently published a paper which demonstrates the contribution of the UK’s nature-rich places to combatting climate change.
We used satellite-derived mapping to locate all the areas in the UK that provide special habitats for nature – species-rich grasslands, ancient woodlands, saltmarshes, heaths and bogs – and estimated how much carbon they store in their vegetation and the top 30cm of the soil.
This turns out to be a rather large number – around half a gigatonne, or 500 million tonnes, of carbon already removed from the atmosphere through photosynthesis. To put this in context, if this entire store were lost, it would be equivalent to nearly four years’ worth of all the UK’s greenhouse gas emissions. In most habitats, this is mostly stored in the organic matter of the soil, the ‘humus’ so beloved of gardeners. Of particular importance are peatlands.
Carbon sequestration as a result of condition
But knowing how much carbon in these places tells only half the story. We also looked at the influence of the ecological condition of these habitats on their ability to sequester and safely store carbon. We had a particular focus on peatlands (bogs and fens). These are havens for wildlife and are home to distinct and threatened plant and animal communities.
Sphagnum mosses hold water in their spongy forms and help prevent the decomposition of vegetation (c) Mike Pennington
Moreover, compared to most soils, peat is unusual because it forms on continuously wet ground. This means that decomposition of vegetation, which normally happens (like compost) in the presence of oxygen, has to happen underwater in the near-absence of oxygen and so it occurs a lot slower.
In most ‘mineral’ soils, the speed of plant remains decomposition means the soil holds around 6-10% organic matter (the rest being inorganic material derived from rocks and living material). In peat soils however, the slow decomposition rate means that much more organic matter remains (often 30% or more) and accumulates – sometimes until the soil carbon store ends up many metres deep.
However, if peat gets dry (through drainage or other damage), decomposition speeds up and this carbon is released back to the atmosphere as CO2. If bogs and fens dry out, their vegetation changes as well. Typical vegetation of wet peatlands (like reeds or Sphagnum mosses) is replaced by grasses and heather in drained peatlands, but it is only the wetland vegetation that makes peat.
It might sound strange, but peatlands are one place where planting trees doesn’t make sense, because their establishment causes the soil to dry and to lose carbon, more than compensating for the carbon accumulated in the trees.
The importance of peatland
This link between the wetness of peatlands, their vegetation communities and exchange of carbon with the atmosphere has a big influence on carbon stores. We have estimated that all the trees and soil in nature-rich habitats in the UK draw a net 8 million tonnes of CO2 out of the atmosphere each year – equivalent to the annual emissions of 4 million cars (12% of all the UK’s cars).
RSPB Forsinard, a blanket bog in good condition © Andy Hay (rspb-images.com)
However, this public good could be up to 14 million tonnes a year, if large amounts of CO2 were not released back to the atmosphere again through the decomposition of dry peat. This loss could be reversed by restoration of degraded peatlands, blocking drains and revegetating eroded peat, as is being done in the South Pennine Moors.
There is much talk of the UK achieving net zero by 2045, and just as much talk of how planting millions of extra trees will help to achieve this ambition. Trees definitely have a huge role to play in this challenge. Increasing the cover of native species in the right places would probably have great benefits for biodiversity too.
But, let’s not underestimate the huge contribution that could be made by getting our important places for wildlife into good condition – not only would this help achieve their original objectives for wildlife, but it would also make a significant dent in our carbon target before a single new tree needs to grow. Habitat restoration would also have a significant influence on our wilder places. If we don’t want to lose more of these, we must also be careful where we put our ‘extra’ trees.
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