WIRL MSc graduate Alex Foster applied an interdisciplinary approach to assess long-term anthropogenic impacts on domed peatlands using Alfred Bog as a case-study. Changes in the peatland’s areal versus volumetric reduction, the impacts of specific anthropogenic drivers and the supply of three ecosystem services (ESs) (carbon storage, food production, peat production) were examined over 11 dates covering 200+ years (1800-2014). Numerous historical records (air photos, maps and texts) were compiled, processed and interpreted to map and quantify multidimensional (i.e. 2D and 3D) changes using GIS. The approach tackled two hurdles in examining human-induced impacts on peatland structure: spatial and temporal data gaps. Spatial analyses often rely on area or areal proxies alone since peat depth records are less accessible. Similarly, temporal assessments face missing or inconsistent long-term data records, which complicate maintaining finer resolution analyses over extended timeframes. Given depth profile variations within domed peatlands and their incremental reduction over extensive timespans, the potential divergence in multidimensional responses to disturbances both spatially and temporally required further examination.

Spatial Findings:

Changes in area versus volume diverged for both the peatland’s reduction and the impacts of individual drivers. Individual drivers were distinct in their effects on reduction (i.e. spatial distribution, magnitude of areal versus volumetric divergence, average depths and volumetric impacts per hectare) reflecting the value of their differentiation. The distributions and specific progressions of drivers relative to the depth profile resulted in their unique areal versus volumetric divergence and effects on ES supply. That the two main drivers (farmland conversion and commercial peat extraction) differed significantly in their extent, yet yielded similar impacts on peat volume and carbon storage exemplifies this point. Their specific properties and multidimensional impacts would not be captured examining aggregate reduction alone. Thus, a driver-specific examination can improve understanding the diverse effects of different societal pressures on peatlands and their ES supply.

Three-dimensional changes and the supply of associated ESs could not be inferred through areal proxies alone, given that disturbances with significant differences in extent could yield similar 3D impacts. Cumulatively, over half Alfred Bog’s original volume and carbon store remained intact in less than half of its pre-disturbance area. Thus, including spatial variations in peat depth and volume enables a more comprehensive understanding domed peatlands’ structural and functional responses to disturbances than through areal analysis alone.

Temporal Findings:

Multiple dates revealed key trends that would remain undetected in coarser or cumulative analysis of changes. Finer intervals helped capture the dynamic disturbance progression and changes in 2D vs. 3D divergence with incremental reduction. Although exploitation was more extensive in the 19th century and potentially spurred greater changes in area-based ESs such as carbon sequestration, erosion control and habitat support, losses in volume-based ESs such as water and carbon storage were greater in the 20th century.    These shorter intervals also helped identify influential factors affecting specific drivers (e.g. zoning, market values and techniques) and broader disturbances (e.g. mechanization and commercialization of exploitation or increased conservation awareness in mid and late 20th century respectively) over time. In domed peatlands, where exploitation over decades and centuries is common, such factors may fundamentally alter their relationships with ESs. Finer intervals were also necessary to accurately differentiate the impacts of drivers.  Establishing trends using only the pre-disturbance and present conditions not only precludes temporal analysis of changes, but can misrepresent the impacts of specific drivers (e.g. misclassifying and by extension underestimating ‘Commercial Peat Extraction’ sites that were converted to ‘Farmland’ as ‘Direct Farmland Conversion’). Therefore, in domed peatlands that were incrementally exploited by multiple drivers, finer temporal intervals between maps (ideally match the minimum operational timeframe of examined drivers) are necessary to distinguish their effects on ES supply.

Summary:

The historical case-study demonstrates the importance of multidimensional and finer temporal analyses in examining anthropogenic impacts on domed peatlands. The combination of additional spatial parameters (volume and depth profile in addition to area) with an extended temporal analysis, namely over 200+ years provided a comprehensive foundation to assess ES supply and trade-offs with disturbances at Alfred Bog, an approach that could be extended to other domed peatlands, and potentially other sub-classes and sites.

Support:

This research was made possible through support from PCI Geomatics for use of its Historical Airphoto Processing (HAPs) software, and South Nation Conservation, providing key contacts and historical air photos.