Using drones to monitor wetlands
By Melanie Brown
Wetlands, often referred to as ‘kidneys of the land’, are complex systems which provide crucial environmental functions by acting as flood control, filtrating water, and supporting a variety of flora and fauna adapted specifically to wetland environments.
Such complex and functional ecosystems can be incredibly sensitive to change, and the response of vegetation can indicate whether surrounding land use or hydrological change is having an effect on a wetland.
The sensitivity of these systems can make them somewhat difficult to monitor, not just because of the more-than-occasional loss of gumboots in unexpectedly deep bogs, but because sometimes walking through a wetland to monitor its health can be a damaging process for the vegetation, particularly if summer and winter monitoring is required over a period of years.
The use of drones has become a key tool for several Boffa Miskell ecology and biosecurity projects.
Tracking through wetlands can contribute to the spread of weeds, trampling of fragile plants, and disturb feeding and nesting wetland birds. So, what is the best way to monitor a sensitive wetland over time without damaging it?
With the current rate of technological advancements, there are tools available to ecologists that were previously unrefined, extremely expensive, or simply never existed before. The use of drones has become a key tool for several Boffa Miskell ecology and biosecurity projects over the past few years thanks to Boffa Miskell’s Technical Services team, as they are now able to quickly gather high definition images over large areas of difficult terrain.
The high definition images or video footage from a drone flyover can be used to identify spots among healthy planted wetlands which may require a few more plants.
The resulting images can show large-scale patterns in the environment which aren’t visible on foot, and the addition of a multi-spectral lens or LiDAR (topography) sensor on a drone can add even more valuable information to collected data. A multispectral lens records in different light wavelengths which can identify things like chlorophyll in vegetation, giving an indication of plant cover, plant health, and moisture levels, while topographical information is extremely useful for deducing delineations of vegetation communities, and creating 3D ‘flyover’ videos using point cloud data.
One instance in which drone imagery has been used is at Mackays to Peka Peka Expressway north of Wellington to monitor success of plantings in created mitigation wetlands.
The high definition images or video footage from a drone flyover can be used to identify spots among healthy planted wetlands which may require a few more plants to fill in bare space, or an area of weeds which needs controlling. Using this method, an entire wetland canopy can be surveyed in a short amount of time without disturbing the wetland, and without missing any areas that are difficult to access on foot.
Boffa Miskell’s Technical Services is now able to quickly gather high definition images over large areas of difficult terrain.
A lake in the Auckland region is surrounded by a large wetland system which would be too large to effectively survey on foot. The vegetation in the wetland is subject to annual drone flyovers carried out by Boffa Miskell so that our ecologists can map changes in vegetation and wetland size over time. This data can be used as a proxy for wetland health. For example, if a species such as bracken (which tends to grow in drier areas) reduces in area over time and is replaced with raupō, which only grows in permanent water, this would indicate a change in water levels within the wetland. Pair this with the multispectral lens’ ability to map chlorophyll in plants, and you’re able to see if certain species are dying off and being replaced by others.
Certain cameras are even able to pick up soil moisture levels, which are particularly useful for determining the extent (and long-term change in extent) of a wetland.
While there are occasions where there is no substitute for an ecologist immersing themselves in a wetland (quite literally) to retrieve soil samples or survey plant species under the canopy, drones have proved to be very useful tools for gathering information that can’t be seen simply by standing within or next to the wetland.
With the continual innovation of drone technology and Boffa Miskell’s enthusiasm to remain at the forefront of using drones creatively, there is no doubt that there will soon be even more wonderful ways to monitor all sorts of ecosystems on the horizon.
Melanie Brown is an ecologist at Boffa Miskell.