Newly planted trees are growing into the woods of Nieuwe Driemanspolder (reclaimed land in the Netherlands). Photo: Shutterstock
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To restrict CO₂ emissions, it is important to know exactly what volumes of greenhouse gases are being released and what volumes are being sequestered again, for example in forests and farmland. Researchers at Wageningen University & Research are involved in a European endeavour to develop a clear-cut, objective measurement system that can be used anywhere in the world.
A 55 per cent reduction in emissions of greenhouse gases by 2030 compared with the level in 1990: that is one of the main objectives in the new European Climate Law that came into effect on 30 June 2021. The reduction in greenhouse gases such as CO₂ was agreed in the Paris Climate Agreement. The European Union wants to play a pioneering role in the implementation of that agreement. To restrict CO₂ emissions, it is important to know exactly what volumes of greenhouse gases are released and what volumes are sequestered again, for example in European forests and soil. At present, keeping track of the greenhouse gases from fossil fuels is relatively simple as the amounts of oil and petrol used in factories, power plants and transport, for example, are recorded in economic statistics. The situation for farmland and forests is somewhat more complicated.
WUR is planting new trees in Venray, the Netherlands. Photo: Gert-Jan Nabuurs
Felled trees sequester CO₂ for dozens of years, or sometimes even for centuries. Photo: Gert-Jan Nabuurs
Trees grow in the summer, and sequester CO₂ as they do so. But what happens if some of the trees are felled? If that wood is used for furniture or timber construction, the carbon remains sequestered for decades or even centuries. If the wood is burned, the CO₂ is released again. But that also saves on fossil fuels. What is more, there are differences between different kinds of forest (commercial forests versus primeval forests, for instance) and trees (fast-growing versus slow-growing). The situation varies per hectare, per tree and per season. And all those differences have an impact on the amount of CO₂ that is sequestered or released. A healthy forest will grow by about 3 per cent per annum, as the existing trees become taller and wider and as new trees appear. That increase in the amount of wood is one way in which nature captures carbon. But carbon is not just sequestered in the wood: some of the foliage, which also contains carbon, decays while the rest is absorbed permanently into the soil. The soil in forests is an important and significant repository of carbon dioxide due to the absorption of carbon over many years.
As regards farmland, vast amounts of carbon are sequestered in the growing season and then released in the winter as crops are harvested. These annual fluctuations are excluded from the calculations as the net effect is assumed to be negligible: the amount sequestered is about the same as the amount released. However, there are ways of storing additional carbon in the soil through sustainable soil management. This means that decisions about how to use farmland affect the net amount of carbon stored in the soil.
A new online map shows the powerful impact of forests on local and global scale. How much carbon do forests actually take up? Where is deforestation happening? Prof. Martin Herold explains why these maps are so important for global climate control.
In 2023 and 2028, assessments will be made of the annual flows of CO₂ and other greenhouse gases (emissions and sequestration) for the world as a whole to determine whether the current measures to reduce emissions are sufficiently effective to meet the climate targets. However, the approach used varies between countries, says Mart-Jan Schelhaas, a researcher at Wageningen University & Research (WUR) who is responsible for the assessment of forests for the Netherlands. “The methods used within the EU are reasonably harmonised, but different methods and models are often used outside the EU. In permanently forested areas such as in Russia, different models are used that produce different figures. There are also major economic interests at stake, which is why people have doubts whether the UN models are sufficiently impartial.”
That is why the European Commission has set up the VERIFY project. In this project, European researchers are working on an independent verification system for all those models and methods. This system will be applicable throughout the world. Moreover, the verified methods will increase transparency. VERIFY looks at all sectors: not just forestry and farmland but also transport, industry and energy. Schelhaas: “But in Wageningen we are only assessing the forests and farmland. There are not many EU groups able to model all the European forests. That is very much Wageningen’s contribution as this is our area of expertise.”
In forested areas such as in Russia, different models produce different figures
Every tree is different and the situation in every season is different, which in turn affects the amount of CO₂ emissions that forests store or release. Photo: Shutterstock
One method for getting a better understanding of the state of forests and farmland is using satellites. “That lets us look at the land use, disturbances in forests and the CO₂ concentration in agricultural land and forests”, explains WUR professor Martin Herold, who works at the Laboratory of Geo-Information Science and Remote Sensing. “We use a combination of forest measurements, satellite data and models to better estimate how much CO₂ forests absorb and what effect a changing climate has on that.” The professor says that satellites let researchers quickly spot changes in the coverage of forests, for example due to expansion or felling. The combination of satellites and measurements on the ground in forest assessments makes the Wageningen contribution very powerful.
In addition to being an independent system, VERIFY provides information about the CO₂ status much more quickly than the current UN system. The system the EU uses at present only publishes figures about 18 months after that year has ended, whereas VERIFY will be able to produce data the following April. That enables faster adjustments to be made in response to the figures. Furthermore, VERIFY has resulted in new knowledge that Wageningen’s researchers can use to improve their own data and models. For example, it is now possible to zoom in at the provincial level and to get more detailed information, and they know much more about the effect of weather conditions on growth. Another significant benefit for the Netherlands is the improvement in the EU model for forests as that enables better analyses of the timber supply chain, which in turn is important because the Netherlands aims to be a pioneer in the biobased economy.
European research context
VERIFY addresses the following European policy challenge: A reduction of 55 per cent in emissions of greenhouse gases in Europe by 2030 compared with 1990 Wageningen University & Research groups involved: Wageningen Environmental Research, Geoinformation Science and Remote Sensing European and other countries involved: Austria, Belgium, Finland, France, Germany, Ireland, Italy, the Netherlands, Norway, Russia, Sweden, Switzerland, Turkey and United Kingdom
Duration: 2018 – 2022
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