Importance of taking short-term dynamics of forest ecosystem services into account

Static maps are key tools for assessing ecosystem services. Our study shows that hotspots of three boreal-forest services – wood production, bilberry production, and topsoil carbon storage – can change over just 10 years, suggesting that dynamic tools should be used to manage the dynamic forests landscapes.

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It is widely known that forests (Fig.1) are major providers of ecosystem services, including timber, other forest products, recreation, regulation of water, soil and air quality, and climate change mitigation. Thus, assessments of ecosystem services (also termed Nature’s Contributions to People, NCP) are pivotal in policy and land-use planning for sustainable use of forest resources. The main tools for assessing and managing ecosystem services are maps providing snapshots of their potential supply. Such static maps may enable the identification of areas of high or low supply of ecosystem services, or suggest spatial trade-offs and synergies amongst them. Currently, large public resources are allocated to map the supply of ecosystem service at different spatial scales, e.g. over the European Union.

Figure 1. Boreal forest in Finland. Photo credit: Daniel Burgas

A major limitation in the current management of ecosystem services is our poor understanding of how their potential supply changes over short timescales. Forest ecosystem services dynamics result from dynamics of the environment, of the tree species underlying the services, or management actions regulating the levels of the services. These dynamics further lead to constantly changing trade-offs and synergies among ecosystem services through time. Consequently, static maps of ecosystem services may become inaccurate soon after being produced. Static snapshot quantification and mapping of ecosystem services may therefore lead managers to make erroneous inferences about the delivery of services through time, and thus manage ecosystems inefficiently. To effectively manage ecosystem services in landscapes that will constantly change into the future, we must account for how, and at what rates, different ecosystem services change.

The issue of dynamic ecosystem services as a challenge to effective decision-making emerged when Jan Bengtsson, Jon Moen and Tord Snäll, after having contributed to Gamfeldt et al. (2013), were invited to be scientific advisors in the Swedish Environmental Protection Agency’s (SEPA) participation in the Mapping and Assessment of Ecosystems and their Services – MAES. MAES was a technical working group contributing to one of the actions in The EU Biodiversity Strategy to 2020. Our task included contributing to Maes et al. (2016) and a pilot study aiming to show an approach to map forest ES based on statistical modelling and prediction using open data. An executive summary for the nation level was presented in Snäll et al. (2014).

While doing this, Snäll et al. (2014) took the opportunity to highlight that the ecological processes underlying the ecosystem service levels are complex and that synergies and trade-offs amongst them are not reflected on static maps. Following up on our recommendation, the SEPA funded some extra work to demonstrate this limitation of maps. Our work would be part of the SEPA contribution to the MAES work and further provided knowledge towards achieving Sweden's environmental objectives. Snäll, Bengtsson and Moen met and outlined the specific questions to be answered. Louise Mair, who was a postdoc in Snäll’s group, got involved and started up the analyses. Later also María Triviño got involved and she further contributed to writing the paper and the analyses. The Snäll-Triviño collaboration had recently started with their joint FutureBioEcon project on projecting forests, ecosystem services and biodiversity given scenarios of future forestry and climate and their collaboration in the project "Spatial dynamics of ecosystem services and biodiversity hotspots in boreal forests" led by Triviño and funded by KONE foundation.

This collaborative effort led to our study published in Nature Sustainability, in which we show that three key forest ecosystem services: wood production (Fig. 2), bilberry production (Fig. 3), and topsoil carbon storage (Fig. 4) were highly dynamic. Almost 85% of the sites with low levels and 65% of the sites with high levels for these ecosystem services had changed into a different level over a ten-year period. Wood production showed higher rates of short-term dynamics than bilberry production and carbon storage.

Figure 2. Timber production. Photo credit: María Triviño.
Figure 3. Bilberry production. Photo credit: María Triviño.
Figure 4. Topsoil carbon storage. Photo credit: Jan Bengtsson.

Our conclusions are based on first categorizing sites as having ‘high’, ‘medium’ and ‘low’ levels of the services. Next, we investigated how the sites changed categories from one point in time into another one ten years later.

We also investigated how hotspots (defined as sites with high levels for all three of the ecosystem services) and coldspots (low levels of all three services) changed over time. Such hotspots and coldspots are of particular interest for ecosystem service assessments. We found that hotspots and coldspots of these services changed into another category during the ten-year study period, and these changes were generally higher than for individual services.

In a time of intensive resource exploitation and climate change, the capacity of ecosystems to sustain many services and goods to society is uncertain. The ultimate goal of managing ecosystems should be to assure and maintain the supply of multiple ecosystem services across space and through time. However, the high rate of short-term dynamics of the hotspots and single services challenges such optimization of supply of ecosystem services.

A limiting factor to adopting more dynamic and spatial approaches for ecosystem services management can be the lack of predictive models for how ecosystem services of interest respond to changes in abiotic and biotic conditions or management. We therefore advocate allocating more resources to research on the processes driving both the short- and long-term dynamics of ecosystem services. We argue that there is a need for a transition towards more frequent use of dynamic tools and perspectives in the European Union and global post-2020 biodiversity and ecosystem services policy supporting frameworks, such as the EU Biodiversity Strategy for 2030.

This text was prepared by Tord Snäll and María Triviño. We would like to thank Jan Bengtsson, Louise Mair, Hannah Östergård Roswall and Daniel Burgas for feedback on an earlier version of this post, and the authors for the pictures.

References:

Gamfeldt, L., et al. Higher levels of multiple ecosystem services are found in forests with more tree species. Nat. Commun. 4:1340 (2013).

Maes, J., et al. An indicator framework for assessing ecosystem services in support of the EU Biodiversity Strategy to 2020. Ecosyst. Serv. 17: 14–23 (2016).

Snäll T, Moen J, Berglund H, Bengtsson J. Mapping and assessment of ecosystems and their services – the Swedish forest pilot. Rapport 6626, Naturvårdsverket. Bromma. (2014).

María Triviño

Researcher, University of Jyväskylä