Unsustainable human exploitation has resulted in the degradation of peatlands worldwide (Joosten and Clarke, 2002). The drainage of peatlands results in short-term benefits such as agricultural production, but also causes long-term problems such as soil subsidence, emission of greenhouse gasses, loss of biodiversity, and increasing management costs (Bragg and Lindsay, 2003; Van Hardeveld et al., 2018). To arrest and reverse the unsustainable exploitation of peatlands, management strategies must address the complex interrelations between their biophysical dynamics and their socio-economic context.

The Dutch peatlands are a prime example of drained peatlands which are faced with multiple long-term problems and the challenge of implementing a more sustainable management. In response to this complex challenge, experimental collaborate adaptive management strategies are increasingly put into practice. The building blocks for these experiments reflect wetter conditions which can preserve the peat, such as (a) increasingly higher surface water levels, (b) novel applications of field drains, and (c) a transition in land use from dairy farming to paludiculture, i.e., the cultivation of species such as Common reed (Phragmites) and Bulrush (Typha) in permanent wet conditions. Although these experiments increase our knowledge of the effects of these adaptations, a clear understanding of implementation pathways is still lacking. The design of implementation pathways requires an integrated assessment of time-and-place specific peatland conditions and feasible management options with a fair distribution of costs and benefits.

The RE:PEAT tool (Van Hardeveld et al., 2019) is especially suited to deal with complex challenges like this. It simulates time-and-place specific effects of interventions and provides support for the negotiation processes needed to design pathways towards sustainable peatland management. In this paper, the RE:PEAT tool is used to contribute to our understanding of feasible implementation pathways for adaptive peatland management. The illustrative context for this endeavour is Polder Zegveld, a Dutch peatland polder of 18 km2 located between the cities of Amsterdam, Rotterdam and Utrecht. The questions we seek to answer are: (1) What are the major short-term and long-term impacts of adaptive management strategies? (2) How can the costs and benefits of the management strategies be fairly distributed among the stakeholder groups?

The RE:PEAT tool is embedded in the Tygron Geodesign Platform (TGP), an interactive software platform for 3D modelling of spatial development projects. The TGP integrates a broad range of spatial data and allows the user to combine these data with practical and scientific knowledge. For example, RE:PEAT combines spatial explicit data on soil properties and groundwater tables with an empirical soil subsidence equation (Van den Akker et al., 2008). As a result, spatially and temporally explicit assessments can be made of the integrated dynamics of water management and soil subsidence, including a broad range of societal costs and benefits. See Van Hardeveld et al. (2019) for further details.

In this research, we assessed the following impacts of adaptive management strategies: (a) soil subsidence, (b) management cost of the water system, (c) management costs of the infrastructure of roads and sewers, (d) damage to the foundations of real estate, (e) Net Value Added of agriculture, (f) terrestrial emission of greenhouse gasses, and (g) expected dominant type of vegetation in the drainage ditches. Regarding impacts (b)–(e), we used empirical data provided by the water authority, the municipality, and the local farmers to calibrate the simulation parameters of RE:PEAT to the local conditions. Regarding the emission of greenhouse gasses, we used the equations of Van den Akker et al. (2008) to assess the emission of CO2 and the equations of Cauwenberg et al. (2011) to assess the emission of CH4 and N2O.

We assessed the impacts in the years 2025, 2050, 2075, and 2100 of the business-as-usual strategy (1) and two adaptive peatland strategies (2 and 3):

Current surface water levels, which reflect the business-as-usual strategy. The surface water levels are maintained at 30–70 cm below the ground surface and must be lowered periodically to compensate for the soil subsidence.

The management strategies result in marked variations in the spatial patterns of soil subsidence, ranging from several cm at locations with shallow groundwater tables and/or thick clay deposits, more than 80 cm at locations with deeper groundwater tables and/or thin clay deposits (Fig. 1). The application of pressurized field drains effectively reduces the cumulative soil subsidence compared to the other two strategies at most locations, except the small village in the centre and several non-agricultural plots on which no field drains were installed.

The management strategies also result in marked temporal trends (Fig. 2). Compared to the business-as-usual strategy pressurized field drains will reduce soil subsidence in the short-term as well as the long-term, whereas progressively higher surface water levels will reduce soil subsidence in the long-term only (Fig. 2a). As a result, the scenario with pressurized field drains results in marked lower management costs for subsiding infrastructure of roads and sewers (Fig. 2c), a higher Net Value Added for agriculture (Fig. 2e), lower emissions of greenhouse gasses (Fig. 2g), and higher percentages of ditches with good water quality, i.e., with a dominance of submerged rooted vegetation over duckweed and algae (Fig. 2h).

For all scenarios, the damage costs to real estate are markedly higher in the short-term than in the long-term (Fig. 2d) because at present, the foundations of 33 % of the houses are already damaged. In the scenarios with current surface water levels (1) and pressurized field drains (3), there is little incentive for farmers to switch from dairy farming to paludiculture (Fig. 2f). In the scenario with progressively higher surface water levels (2), the Net Value Added for dairy farming will drop from EUR 919 to 558–593 per hectare in 2100. As a result, 24 %–36 % of the farmland will switch to paludiculture. This explains why the trend in Net Added Value of this scenario does not continue downwards but stabilizes at EUR 600–700 per hectare.

Pressurized field drains will reduce soil subsidence in the short-term as well as the long-term, resulting in marked lower management costs, a higher Net Value Added for agriculture, lower emissions of greenhouse gasses, and better water quality. Progressively higher surface water levels will reduce soil subsidence in the long-term, resulting in a lower Net Value Added for dairy farming and a transition of 24 %–36 % of the farmland to paludiculture.

The costs of the adaptive management strategies amount to EUR 425–478 per hectare per year in the long-term. In the short term, the financial benefits for farmers, the municipality and the water authority are too small to cover these costs. Therefore, implementation of the adaptations will only be feasible if the non-financial benefits of improved water quality and reduced greenhouse gas emissions are considered. A subsidy of EUR 38–188 per reduction of 103 CO2-equivalents would cover all implementation costs.

The implementation of adaptive management strategies requires more certainty regarding the effects of the adaptations and additional features of the RE:PEAT tool. This will improve decision support for peatland management and facilitate adaptive management strategies that will contribute to a more sustainable peatland management.