Abstract
The scale and ambition of the Scottish Government investment in peatland restoration requires efficient and cost-effective methods for large area monitoring and reporting of peatland condition. Monitoring and reporting are required to inform peatland restoration priorities, quantify outcomes, and identify and minimise risks. Monitoring and reporting of peatland condition is also a crucial component of balancing the provision of onshore renewable energy on peatland with peat restoration outlined in the new National Planning Framework 4 (Scottish Government, 2023).
To extend and enhance large-scale monitoring and reporting of peatland condition, the University of Nottingham and the University of the Highlands and Islands with support from NatureScot Peatland ACTION have, since 2017, developed objective, quantitative methods that use satellite measures of peatland surface motion to assess peatland condition. This work contributes to the Peatland ACTION Partnership Monitoring Strategy which has the overall aim of assessing the effectiveness of the Partnership’s work to restore Scotland’s degraded peatlands. The InSAR approach developed here sits within the “Supporting Priority: Develop new tools to improve peatland monitoring”.
Alternative optical remote sensing methods for the analysis of peatland have been developed (Lees et al., 2018) over many years. However, the measures derived from optical imagery, although providing a valuable indicator of ecosystem health, have not proved sufficiently sensitive to spatial and temporal changes in peatland condition. Frequent cloud cover also results in a discontinuous and mosaicked optical record.
Methods using backscattered synthetic aperture radar have also been developed to quantify water table depths (Lees et al., 2021; Toca et al., 2022) but struggle to provide improved sensitivity to peatland condition when compared to optical methods (Räsänen, Tolvanen and Kareksela, 2022). The conclusion of Räsänen, Tolvanen and Kareksela (2022) was based on a rigorous statistical analysis of the ability of C-band SAR backscatter, optical and combined methods to predict water table depth over a range peatland conditions and restoration stages. Räsänen, Tolvanen and Kareksela. (2022) observe that although some methods work very well on some sites no single method is suited to all peatland classes and optical methods generally outperformed SAR backscatter. Little advantage was found in combining methods and a generally poorer performance of all methods was noted on restoration sites. One reason for the variable performance of SAR backscatter is the weaker response with increasing water table depth. However, Räsänen, Tolvanen and Kareksela (2022), note that better performance may be possible using longer wavelength L-band SAR. Unfortunately, commercially available L-band data is more expensive than the freely available C-band data from the European Space Agency.
Surface motion, as measured by interferometric synthetic aperture radar, is sensitive to changes in the ecological and hydrological state of the peat observed on the ground (Alshammari et al, 2020; Bradley et al., 2022; Marshall et al. 2022). The reason for this is that surface motion is a direct and rapid response to changes in water storage and therefore displays a strong response to wetting and drying that precedes changes in plant functional type (Mahdiyasa et al., 2023). For example, following rewetting, swelling of the peat and a reduction in the rate of subsidence will occur before changes in vegetation.
Surface motion measures therefore add a new dimension to the analysis of peat condition by providing measures of the physical behaviour of the peat that are unobtainable by other remote sensing methods. Long-term trends indicate whether peat is subsiding, stable or growing. Seasonal amplitudes indicate the softness, water table depth and hence resilience of the peat. Timing of seasonal peaks indicates the water storage capacity and sites of water accumulation within a landscape.
The use of satellite radar has a distinct advantage over optical satellites because the microwave signal penetrates cloud cover providing repeated regular measures all year round. Data is usually acquired for each area every 6-12 days, with the majority of the data acquired every 6 days.
This report summarises the application of these surface motion methods to an area of 12,800 km2 (Figure 1) containing approximately 680,000 ha of peat. The report provides guidance on the interpretation of the data products and illustrates this via twelve case studies. The GIS spatial data outputs of the work are available for download.
To extend and enhance large-scale monitoring and reporting of peatland condition, the University of Nottingham and the University of the Highlands and Islands with support from NatureScot Peatland ACTION have, since 2017, developed objective, quantitative methods that use satellite measures of peatland surface motion to assess peatland condition. This work contributes to the Peatland ACTION Partnership Monitoring Strategy which has the overall aim of assessing the effectiveness of the Partnership’s work to restore Scotland’s degraded peatlands. The InSAR approach developed here sits within the “Supporting Priority: Develop new tools to improve peatland monitoring”.
Alternative optical remote sensing methods for the analysis of peatland have been developed (Lees et al., 2018) over many years. However, the measures derived from optical imagery, although providing a valuable indicator of ecosystem health, have not proved sufficiently sensitive to spatial and temporal changes in peatland condition. Frequent cloud cover also results in a discontinuous and mosaicked optical record.
Methods using backscattered synthetic aperture radar have also been developed to quantify water table depths (Lees et al., 2021; Toca et al., 2022) but struggle to provide improved sensitivity to peatland condition when compared to optical methods (Räsänen, Tolvanen and Kareksela, 2022). The conclusion of Räsänen, Tolvanen and Kareksela (2022) was based on a rigorous statistical analysis of the ability of C-band SAR backscatter, optical and combined methods to predict water table depth over a range peatland conditions and restoration stages. Räsänen, Tolvanen and Kareksela. (2022) observe that although some methods work very well on some sites no single method is suited to all peatland classes and optical methods generally outperformed SAR backscatter. Little advantage was found in combining methods and a generally poorer performance of all methods was noted on restoration sites. One reason for the variable performance of SAR backscatter is the weaker response with increasing water table depth. However, Räsänen, Tolvanen and Kareksela (2022), note that better performance may be possible using longer wavelength L-band SAR. Unfortunately, commercially available L-band data is more expensive than the freely available C-band data from the European Space Agency.
Surface motion, as measured by interferometric synthetic aperture radar, is sensitive to changes in the ecological and hydrological state of the peat observed on the ground (Alshammari et al, 2020; Bradley et al., 2022; Marshall et al. 2022). The reason for this is that surface motion is a direct and rapid response to changes in water storage and therefore displays a strong response to wetting and drying that precedes changes in plant functional type (Mahdiyasa et al., 2023). For example, following rewetting, swelling of the peat and a reduction in the rate of subsidence will occur before changes in vegetation.
Surface motion measures therefore add a new dimension to the analysis of peat condition by providing measures of the physical behaviour of the peat that are unobtainable by other remote sensing methods. Long-term trends indicate whether peat is subsiding, stable or growing. Seasonal amplitudes indicate the softness, water table depth and hence resilience of the peat. Timing of seasonal peaks indicates the water storage capacity and sites of water accumulation within a landscape.
The use of satellite radar has a distinct advantage over optical satellites because the microwave signal penetrates cloud cover providing repeated regular measures all year round. Data is usually acquired for each area every 6-12 days, with the majority of the data acquired every 6 days.
This report summarises the application of these surface motion methods to an area of 12,800 km2 (Figure 1) containing approximately 680,000 ha of peat. The report provides guidance on the interpretation of the data products and illustrates this via twelve case studies. The GIS spatial data outputs of the work are available for download.
| Original language | English |
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| Publication status | Published - 13 Jun 2025 |