Mapping of forest damage, using drones

Last summer, a drone with a multispectral camera was often seen to fly over one a spruce forest in Kymenlaakso. We used the Drone to gather information on how a Spruce bark beetle infestation was proceeding during the season.

This data collection was part of the InnoForestView project, aiming at finding new tools to help identifying and assessing the effects of vectors involved in forest and tree damage. We carried out planned experiments in Luke's Punkaharju research forests. In addition, we used natural sites such as the one in Kymenlaakso.

The Drone recorded the process of spruce bark beetle attacks, where a part of a lush green spruce forest gradually turned into a forest with dead trunks. In a small area, at least 70 large spruces died during the season and after a storm, dozens of trees had fallen.

Everything affects everything in the forest - the change and variation of weather conditions, strong winds and the mild winters stress forest trees. Already weakened trees are then exposed to other damage. This was also the case with this forest. On the edge of a clear cut area, spruces were exposed to the sun, wind, and eventually to the bark beetle. With careful forest management, risks can sometimes be reduced, but much is also left to chance. This highlights the need to monitor the damage.

There are tools for up-to-date monitoring that serve different needs depending on the extent and visibility of the forest damage. The largest forest damage sites can be found outside Finland. The European Union's contribution to the Copernicus Earth Observation Program, and in particular to its Sentinel satellite series, has made a huge amount of new information freely available.

Channels of Sentinel-2 satellites range from visible light to infra-red (NIR and SWIR), and cover the whole of Finland twice a week. A handy resource to check out these images is the Sentinel Hub. In our InnoForestView project, our Russian partners also worked with Russian satellite systems such as Resurs, these data are not so widely known.

While the data brought available by different satellites has increased, also data processing is now possible for more and more people. For free software such as Quantum GIS (QGis), there are freely downloadable add-ons for satellite image analysis. Google's Earth Engine programming environment (GEE, https://earthengine.google.com/) brings an up-to-date large satellite imagery database easily available to the coding community.

Compared to satellite images, drones are able to quickly gather very accurate local information. Equipped with accurate GPS devices and a multispectral camera, one can create a three-dimensional model from which trees and their canopies can be distinguished. The reflectance of sunlight by each tree can be analyzed with the accuracy of a leaf! Symptoms of pests, such as weakened canopies, can thus be identified, even if the actual cause cannot be determined from the image alone.

Drone images can also be used together with satellite images to make the interpretation of the satellite image more accurate, even from sites that the drone did not visit. The drone is also suitable for continuous monitoring of the damage site, for example, when information is needed on how quickly the damage is spreading in the area.

The InnoForestView project will end soon, and it is time to pull the lessons together. We did not solve everything – circumstances and information needs vary, and patent solutions are not always found.On the 26th of May we will present our findings at the joint webinar of the Biokarelia and InnoForestView project. Welcome to the webinar! (Registration & more information at https://kareliacbc.fi/fi/node/1841)

Research is moving in interesting directions, and different approaches for damage mapping are being assessed. For example, the ability of dogs to smell bark beetle infestations seems promising. And how is the development of drone technology – when do we see that drones will be in practice harnessed for targeting pest control?

InnoForestView project is part of the South-East Finland - Russia CBC program (CBC 2014-2020). The program is funded by the European Union, Finland, and Russia.