Peat bogs are worth saving. They are a specific type of naturally formed environment dominated by acidic partially decomposed peat 'soil' and acid tolerant vegetation - notably mosses. Ideally, these bogs are very wet places. Over time, humans have plouged the surface of bogs to reclaim the land, typically grazing or silvicuture. Ploughing the bogs has the effect of increasing standing water outflow - drying them out.
While some (typically less productive) land can be reclaimed by this method, there are horrible consequences. By draining the water you allow the peatland to dry, which leads to a collapse of the established ecosystem. In biological terms, mosses lose suitable habitat, invading plants from grazers' droppings take hold and exacerbate water removal, and tree planting compresses the subsurface, reducing further the stored water. It's all about the water.
When the peat subsurface dries as the water table is lowered, it is removed from the watery acidic preservative that prevents decomposition. This material interacts with the oxygen, leading to offgassing of significant amounts of Carbon Dioxide and methane gasses. The International Union for Conservation of Nature states:
"CO2 emissions from drained peatlands are estimated at 1.3 gigatonnes of CO2 annually. This is equivalent to 5.6% of global anthropogenic CO2 emissions." [1]
We can use aerial imagery to help understand the current condition of a given peatland, extract data to help guide the management plan and restoration activities. In the case of Allt Ddu, an upland peatland situated in North Wales, LandScan UK were asked to provide a minimum resolution of 4cm, plus information on surface topography
We set our GSD (Ground Sampling Distance) to >2cm/pixel. If you are considering hiring an aerial survey, remember this part! We recommend setting GSD to 0.5x required resolution, to allow for additionals factors, such as weather and lighting.
We took a large number of images (in this case 450+) of the 20 hectare area in question, stitched them together and geolocated them accurately to produce an orthomosiac image, or a picture of everything. Our methods mean we can also extract information of the surface topology, allowing detailed understanding of the landscape before any restorative work is undertaken. This can also help understanding the work that's required, leading to cost control and effective targeting of value-for-money areas on the site before any work is undertaken.
Once this data is collected and analysed, careful visualisation work is undertaken to best enchance the data underneath - it's never the same for any site! Not only is the resulting information detailed and tailored to the clients expectations, we ensure it's beautiful. Perfect for hanging on the wall, or for a gift for your loved ones with land.
The visualised data can then be mined for information. On the orthographic image, we can immediately see a number of plough lines in the southern half of the peatland. Our process allows us to overlay this data in a program like Google Earth Pro, letting anyone quckly and cheaply measure surface features for yourself.
After a short analysis, we were able to identify 5.5km of grips (or plough lines) requiring damming. At roughly £4-6 for a peat dam of this size, and based on an average of 8m spacing, we were able to estimate intially the cost of East-West damming to be £2750-£4125. A specialist will be required to provide further insight to this aspect of the management plan, drone surveys are not sufficient to give the full picture of costs on their own. Further information such as equipment availability and ground suitability need to be taken into account, as well as standard business practices such as timing.
The surface model on the right supports management plan decision making, as well as information on the nature of the bog. With the crest of the land running East-West through the centre, it was advised to the client that dip wells with data loggers would be well placed in a North-South line.
Data loggers will measure the height of the water table continually throughout the year with no manual intervention, perfect for improved data integrity and reduced ongoing monitoring costs - despite the increased intially purchase cost of the unit. We were able to advise the client to place loggers at four critical areas, the crest of the land, near the northern bare peat pattern configuration, the gripped area, and the southern outflow (lowest point).
Going further, we can then do additional analysis on vegetative extent. The left hand image below shows the extent of vegetation featuring a high concentration of chlorophyll (think grasses and reeds in the swampy parts.) The image on the right selects specific wavelengths of the visual spectrum to hightlight the extent of heather (Calluna Vulgaris) across the site. This work provides an invaluable insight into the hydrology and biology of a particular ecosystem.
It is easy to see that when combined with ground-based environmental measurements (such as biodiversity studies), aerial land survey data can dramatically increase the efficacy of your management plans. Call us today to see how we can help.
Signing off,
Jamie