Radar satellite data a “big step forward” for peatland health monitoring

Satellite-derived soil moisture and water table dynamics are helping scientists to monitor peatlands in various conditions in efforts to reduce global greenhouse gas emissions

Peatland covers about 20% of Scotland, providing a unique habitat, filtering our water and storing carbon. But when damaged, peatlands can be a significant source of greenhouse gas emissions.   

In fact, about 80% of Scotland’s peatland is thought to be damaged and contributing to an estimated 13% of the nation’s greenhouse gas emissions. 

Because of this, an increasing amount of work to restore peatlands is being done to return peatland into healthy carbon stores, as well as the unique habitat it provides to a wide range of species. 

But because peatlands can come in a range of sizes, from small pockets in the landscape to vast expanses of blanket bog, it’s not always easy to monitor their condition. 

This is a challenge researchers from The James Hutton Institute in Aberdeen have been investigating. A promising route is the use of radar satellite data, collected by European Space Agency’s (ESA) satellites, to assess peatland condition.

Overcoming the challenges of soil monitoring

Radar instruments can penetrate into the soil, informing us about the moisture conditions in the first few centimetres. This is important – soil moisture is one of the key indicators of whether peatland is storing, or releasing, carbon dioxide and methane, but it’s data that’s not always easy to get.

“Traditionally peatland soil moisture dynamics would be monitored by carrying out field measurements,” explains Dr Linda Toča, a Geospatial researcher at The James Hutton Institute. “This isn’t always easy as peatlands can be very remote, cover vast areas and there are various costs associated with the installation and maintenance of the instruments.

“Being able to use satellite imagery to look at soil moisture or water table dynamics across wider areas and longer time periods gives us a really helpful tool. It can help us to understand the health of our peatlands in Scotland and, in the future, also internationally, helping to improve peatland management and enable the preservation of these ecosystems as carbon sinks at continental scales.”

The technique revolutionising monitoring

Dr Toča has been working on this technique with the Hutton’s Dr Alessandro Gimona and his team who work on wider soil monitoring programmes using various types of satellite data.

The technique Dr Toča investigated uses radar backscatter data from the ESA’s Copernicus SENTINEL-1 satellites. Sentinel-1 is a radar satellite, which means the sensors on it actively emit energy. Once these signals reach the ground, the energy is scattered and a portion of it is reflected back to the satellite’s sensor. The energy that is backscattered will vary based on the moisture conditions in the peatland, which enables us to use satellite data to infer what moisture changes might be happening on the ground. 

“This means we can not only look at current peatland condition, but also adapt this method to monitor the success of peatland restoration projects, look at trends over time and potentially underpin carbon credits that are now starting to be used to finance restoration schemes,” she explains.

The technique was first tested across 11 sites at the RSPB’s Forsinard Flows Nature Reserve, in Caithness and Sutherland, which is part of one of the largest areas of blanket bog in the world. The condition of sites ranged from restored bog to sites that are as close to natural as possible.

“Forsinard is a very unique location with peatland restoration projects dating back to the 1990s, so we can investigate how long it takes for a site to benefit from restoration work and what the impacts of different restoration methods are,” says Dr Toča. “But it is a large area, with the restoration sites spread across 20,000 ha. 

“Traditionally, to get a good indication of peatbog health, we would have to physically travel to sites to assess them, which takes time and resources. Using satellite data could make that work a whole lot easier. Additionally, the data produced from the satellite images will also contribute to climate models to predict future scenarios and show how climate change-induced alterations might impact peatlands and the associated greenhouse gases.”

Expanding the project’s scope globally

Right now, the method is being tested on a wider network of restored peatlands. In collaboration with the Peatland ACTION programme, scientists are applying the system to more than 30 additional sites across Scotland, with plans to expand to mainland Europe and globally.

Project leader Dr Rebekka Artz, a leading peatland ecosystems researcher at the Hutton, says, “Developing radar backscatter-based monitoring of peatland condition is a real achievement. The next step is to scale this up so it can be used internationally, and to link it to other measures of peatland condition that are available to us through satellite and aerial imagery data sources.” 

“This is a big step forward for modelling peatland where there otherwise isn’t much data available for us to work with. This will help us to better understand peatland condition, improve their management and preserve this ecosystem as a carbon sink,” says Dr Gimona. 

As well as exploring the use of radar satellite data to monitor peatland soil moisture, optical satellite data and aerial imagery data are also being used by other researchers at the Hutton to improve mapping and estimate of spatial distribution of peatlands. 

This includes work by Dr Matt Aitkenhead and colleagues looking at better classification of peatland condition on the basis of features in the visible spectrum (optical) of satellite data, such as from Sentinel-2 and automatic extraction of erosion and drainage features. This, along with extensive peatland field data collection, will enable us to build a more holistic view of the status of Scotland’s peatland health. 

Dr Toča’s research titled ‘Potential for Peatland Water Table Depth Monitoring Using Sentinel-1 SAR Backscatter: Case Study of Forsinard Flows, Scotland’ was published in the journal Remote Sensing.

Author

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