European climate scientists warn against placing too much trust in the ability of nature’s carbon sinks to save us from climate change. This is the message from the European Greenhouse Gas Bulletin ‘FLUXES’, published today by the Integrated Carbon Observation System, ICOS.
“The carbon sinks both on land and ocean ecosystems are important, but vulnerable. These sinks have suffered over the years, and still continue to suffer from human actions. Climate change further decreases the ability of the sinks to take up and store carbon. Moreover, the carbon uptake of an ecosystem varies greatly from one year to another, making changes difficult to notice. Reducing fossil fuel use to zero in the next few years is the only option,” says Werner Kutsch, Director General of ICOS, Integrated Carbon Observation System
The EU's total forest carbon sink has decreased by nearly a third during the last decade, which is attributed to harvests and the natural ageing of forests. “Climate change increases the threats to forests. Fires, droughts, insects and other disturbances diminish the forests’ ability to take up and store carbon,” says Dr Manuel Acosta, from ICOS Czech Republic and CzechGlobe.
Forests are often commercially important for countries, which affects their treatment, and when and how they are being harvested or cut. However, many forestry practices, such as clear-cutting, turn a forest into a carbon source. In temperate and boreal regions, it can take up to 15 years until the forest becomes a sink again, and 20-40 years or even more until initial emissions are compensated for. Old forests are vital for carbon storage and biodiversity. The last remaining old forests in the EU should be protected immediately.
Healthy and biodiverse coastal areas store more carbon than urban or polluted coasts
The ocean takes up about 25% of the annual fossil fuel emissions caused by human activity. Large quantities of carbon are stored in healthy coastal vegetation and in the sediments. However, the key word here is ‘healthy’ – about 80% of the coastal habitats in Europe are in poor condition. Climate change is accelerating this loss. “Mature coastal ecosystems have higher biodiversity and take up carbon more efficiently than restored coastal habitats,” says Dr Richard Lilley, Director of Project Sea Grass, which focuses on conserving seagrass ecosystems. Therefore, we must urgently preserve the healthy ecosystems still left, and restore those in poor or in critical condition. “Coastal ecosystems tainted by eutrophication or other human activities, have been shown to emit more carbon dioxide and methane than healthier ones,” adds Dr Alf Norkko lead scientist of the ICOS Tvärminne measurement station in Finland.
There is also a serious lack of ocean data. “We need long-term measurements to understand how and at what rate the coastal ecosystems sequester carbon. We also need to quantify how much greenhouse gase coastal ecosystems emit,” states Dr Norkko.
Carbon removal certification sees potential in soils and forests but results are difficult to verify
The major sources of agricultural emissions are methane from livestock and manure management, and nitrous oxide and carbon dioxide from the soils and their fertilisation. These emissions have not decreased in the last decade. They are hard to tackle by phasing out fossil fuels because their sources are not energy-related. Thus, the Carbon Removal Certification system proposed by EU Commission - and currently being discussed in the European Parliament – not only addresses possible technological solutions and forests but also farming. Dr Werner Kutsch points out, however, that carbon farming methods, which aim to increase the carbon content of the soil, could theoretically compensate for only a small fraction of agricultural emissions. In practice, cropland soils often lose carbon rather than store it. In addition, carbon storage in cropland soils might not be permanent, given that decisions about land management are affected by many factors other than carbon storage potential.
Reliably measuring changes in the soil carbon stocks in a given field is difficult, and possible only over long time periods. If the carbon removal certification is accepted, the EU needs to establish reliable and transparent monitoring for carbon uptake and storage. The ICOS data and the knowledge of ICOS scientists offer great potential to be utilised when creating such a monitoring system for Carbon Removal Certification.
All scientists interviewed by FLUXES highlight that healthy ecosystems are extremely valuable to mankind and the Earth. “The European Green Deal in general and the protection and regeneration of nature, in particular, is conservative politics at its best. They should not be sacrificed to short-term economic interests,” concludes Dr Kutsch.
Read FLUXES here.
FLUXES is an annual publication by ICOS research infrastructure and aims at highlighting topical climate issues to an audience of policymakers, policy advisors, and journalists. The second volume was published on the 6th of July 2023, and the first volume in 2022.