Natural climate buffers combine nature development with water storage and greenhouse gas capture
Due to climate change, there is a growing need to try concepts like the natural climate buffer approach. The approach leads to multifunctional land use. The evaluation of three climate buffer projects highlights the learning points for future projects.
A recent evaluation identified success factors and learning points in the realisation of more than 70 natural climate buffers initiated by the Natural Climate Buffers Coalition (Coalitie Natuurlijke Klimaatbuffers
Dutch water management has gained substantial experience with climate adaptation using natural processes, and the CNK programme ‘natural climate buffers’ is a significant example. CNK defines natural climate buffers as areas where climate policy objectives are achieved by giving space to natural processes that contribute to, among other things, water retention, the prevention of water shortages and the reduction of greenhouse gas emissions, in combination with other spatial functions. The evaluation (Veraart et al., 2019) was carried out with the aim of providing guidelines for implementation of the climate buffer approach in spatial policy.
This article is based on the evaluation of three illustrative climate buffer projects: De Onlanden, Hunze and Anserveld/Leisloot. These initiatives served as a catalyst for new project development by linking water management, nature development and the use of public space. The learning points for future projects are mapped out on the basis of contributions to water storage, greenhouse gas benefits and costs.
The water storage realised and the associated costs have been determined based on available environmental impact assessment research. The costs per hectare and per cubic metre were calculated to provide insight into the cost effectiveness.
The greenhouse gas emission reduction factors used (6 and 24 tonnes ha-1 year-1) were based on emissions measured at comparable locations in the Netherlands with and without elevated water levels. The chosen bandwidth does justice to the spatial and temporal variabilities that play a significant role. A hypothesis has been formulated about the achievable annual greenhouse gas reduction (kilotons), based on the emission factors and the surface of the climate buffer, adjusted for the presence/absence of peat (Figure 1) and the extent of drainage in the original situation (Knotters et al., 2018).
Climate buffers can only be used to generate CO2 Credits for the free market (GDNK, 2018), with the maximum carbon price in 2018 being around €5 tonne-1 CO2-eq (Hamrick & Gallant, 2018). This value was used for the monetarisation of the carbon credits.
De Onlanden (2,500 ha) was a peat area with agriculture (grassland), and an unnatural water level with fluctuations between 0.25 to 0.80 –mv. Growing problems due to soil subsidence and frequent flooding that even threatened the city of Groningen formed the reason for the realisation of a water retention area combined with the development of nature and areas for recreation. After the land acquisition, quays and barriers were constructed in the area, peat pits were dug and the natural water level dynamics were restored.
This climate buffer (approx. 785 ha) concerns a brook valley and consists of three sub-projects: Bonnerklap, Torenveen and Tusschenwater, which were carried out from 2010 to 2019. Besides nature development, peak water retention and water conservation are also important goals. The three sub-projects are complementary to previously implemented nature restoration projects. The project areas mainly involve peat and are partially on marshy soil (Figure 1). Before implementation of the proposed measures, the groundwater levels varied between 0.60 m -mv (winter) and 1.20 -mv in the summer. The average water levels can increase by 0.55 m in both seasons with the taken measures (Spoolder, 2013).
Anserveld/Leisloot (approx. 150 ha) is part of the Dwingelderveld National Park (approx. 4,000 ha). Important objectives included combating the dessication of nature and reduction of flooding risks at Meppel. The hydrological restoration measures have led to rewetting of the heathland and to recovery of wet soil layers that slowly drain excess rainwater. The soil sub-layer consists of boulder clay and surface sand. Peat soil is present locally where the development of growing bog is possible, provided that the groundwater level remains within 0.05 and 0.20 –mv (Schunselaar et al., 2014). Prior to the redesign, the ground-water level was much lower.
Figure 1. Peat and bog areas in the Northern Netherlands Mineral soils (peat layer < 15 cm); Marshy soils (peat layer 15 - 40 cm); Thin peat soils (40 cm > peat layer < 120 cm), thick peat soils (frequently deeper than 120 cm –mv), marsh (no peat) and water.
Table 1 summarises the contributions of the three climate buffers to national climate policies, water management and nature development objectives.
Table 1. Summary of the contributions per climate buffer
The development of nature with peak water storage and water conservation
The discussed imate buffers are examples of successful collaboration between the nature area managers, water boards, provinces and municipalities. The realised water retention (Table 1) concerned a substantial portion (> 20%) of the total water storage needs of the water boards involved and the Dwingelderveld National Park. These projects have contributed to risk reduction for flooding in the surrounding agricultural areas and cities (Groningen and Meppel) together with the realisation of 1,550 ha for the National Nature Network and recreational facilities. Groningen Water Company has invested in water conservation and the development of nature in the Hunze brook valley. The abiotic conditions have been improved for wetland nature (De Onlanden), wet heath and bog (Anserveld) and stream valley nature (Hunze).
Although time series of groundwater levels are available , there are no studies that determine the precise effect of these climate buffer projects on water conservation. The monitoring of hydrology, nature and water quality was inadequately coordinated to quantify the impact on water conservation of climate buffers and the derived advantages and disadvantages for agriculture and nature.
The capture of greenhouse gases in climate buffers
Before constructing the climate buffers, the Hunze and De Onlanden were still partly in use for agriculture and, therefore, a net source of greenhouse gasses. The most optimal hydrological conditions for reducing greenhouse gas emissions have been achieved in De Onlanden. There is a thick layer of peat (Figure 1) in a continuous area (2500 ha) with minimal drainage. In the Hunzedal, the effect per hectare is smaller because there is less peat soil and an optimal increase of water tables is not possible everywhere due to the adjacent agriculture.
In Anserveld/Leisloot, the greenhouse gas emissions in the initial situation were already low (sandy soil). Locally, peat bog development is possible for fens (marginal, Table 1). Wet heathland captures fewer greenhouse gases per hectare compared to peat bog. In all climate buffers, emissions from methane can partly offset the capture of CO2 within the first years (Fritz et al., 2017).
The cost per cubic metre of water retention is a measure of cost effectiveness, and it varies between 2 and 4 €m-3. The interviews show that the benefits of the climate buffer approach were often more decisive for those involved, or that the alternative plan was more expensive (De Onlanden).
At the current market price, the potential financial benefits of carbon capture for the landowner are between €30 - 120 ha-1 yr-1. At a price of €25 tonne-1 CO2-eq or higher, carbon capture is a realistic form of co-financing for the implementation of future climate buffers (€150 - 600 ha-1 yr-1). If the benefit for nature, the drinking water supply and recreation is also translated into financial returns, the feasibility will increase further. When determining carbon credits, financial risks can be made manageable with multi-year agreements (15-50 years).
Natural Climate buffers have been a driving force in realising the development of nature and climate adaptation in an economically efficient way with opportunities for recreation, residential areas and drinking water extraction. Due to climate change, there is a growing need to work with concepts such as the climate buffer approach. Mainstreaming the climate buffer approach in spatial policy offers an opportunity to efficiently implement the administrative agreement on Spatial Adaptation and the Climate Agreement (Ruimtelijke Adaptatie en het Klimaatakkoord).
The objectives is set within the Climate Agreement to reduce emissions up to 1.5 Mton CO2 eq by land use change on mineral soils and peat. About 20 - 30% of this can be achieved with rewetting measures (Vertegaal et al., 2019). The peat meadow area (2,400 km2 in 2004) decreases due to peat oxidation, which leads to soil subsidence. A lot of peat meadow areas can still be saved by using the climate buffer approach.
To get a grip on the financial risks of this type of spatial investment, innovation and the linking of existing monitoring networks are needed for the benefit of an integrated evaluation of climate adaptation, the greenhouse gas capture potential of ‘wet’ nature and the certification of CO2 allowances.
(Wageningen Environment Research)
(the Dutch Society for Nature Conservation)
(Wageningen University AEW chair)
(Wageningen Environment Research)
(De Lynx Communication Agency)
Tim van Hattum
(Wageningen Environment Research)
Michael van Buuren
(Wageningen Environment Research)
* The Natural Climate Buffers Coalition consists of ARK Nature Development, LandscapesNL, Nature and Environmental Federations, the Dutch Society for Nature Conservation, Staatsbosbeheer (a Dutch forest management agency), the Netherlands Society for the Protection of Birds (Vogelbescherming Nederland), the Wadden Association and the World Wildlife Fund. The evaluation was made possible with financing from LIFE IP Delta Nature and the Ministry of Agriculture, Nature and Food Quality or ‘LNV’ (soil map).
The results from three natural climate buffers in the Northern Netherlands, namely De Onlanden, Hunze and Anserveld/Leisloot, are discussed. They have acted as catalysts for new project development in which water management, climate policy, the development of nature and the use of public space have reinforced one another. Due to climate change, there is a growing need to work with concepts such as the climate buffer approach. With rewetting measures, it is possible to achieve 20 to 30% of the challenge outline in the Climate Agreement to reduce emissions by 1.5 Mton CO2 eq by land use change on mineral soils and peat. To get a grip on the financial risks of this type of spatial investment, innovation and the linking of existing monitoring networks is necessary.
CNK, 2014. Natuurlijke Klimaatbuffers - kennis en kansen - interim report 2010-2012.
Fritz, C., Geurts, J., et al., 2017. Meten is weten bij bodemdaling-mitigatie. Bodem, number 2.
GDNK, 2018. Methode voor vaststelling van emissiereductie CO2-eq - CO2-emissiereductie via verhoging grondwaterpeil in veengebieden (‘Valuta voor Veen’), Greendeal Nationale Koolstof Markt.
Hamrick, K., Gallant, M., 2018. Voluntary Carbon Market Insights: 2018 Outlook and First-Quarter Trends. Ecosystem Marketplace, Forest Trends, Washington, USA.
Hazelhorst, H.J., 2014. Maatregelenstudie droge voeten 2050 (pp. 90), Waterschap Noorderzijlvest.
Knotters, M, et al., 2018. National, up-to-date information on groundwater levels, digitally available H20 magazine, Online (November 2018), number 11.
Schunselaar, S., et al., 2014. Anserveld - Substantiation of GGOR and WB21. Groningen, Grontmij.
Spoolder, M., 2013. Natuurontwikkeling Bonnerklap. Assen, Grontmij.
Veraart, J. A., Klostermann, J. E. M., Sterk, M., Janmaat, R., Oosterwegel, E., van Buuren, M., & van Hattum, T., 2019. Heel Nederland een natuurlijke Klimaatbuffer: evaluatie en vooruitblik. Wageningen Environmental Research.
Vertegaal, P., Borren, W., & Schouten, B.C., 2019. Natte natuur in het klimaatakkoord – win win in het kwadraat. Vakblad Natuur Bos Landschap
^ Back to start