Remote sensing technology allows us to obtain information from any spot on Earth without having to be physically there. Thanks to this science, we can gather empirical data to face the most pressing challenges that affect our planet – we can do so in an extraordinary way: making the invisible visible, capturing on cartography and images those elements that cannot be caught by the human eye.
Through satellites, drones or airplanes, Earth Observation (EO) allows us to monitor the changing features of the Earth. This can range from the impacts of a flood, volcanic eruption, melting glaciers year after year to the severity of pests, fires or forest droughts. There are hundreds of applications for remote sensing and all of them have great potential for industry, academia or political decision-making. In the case of forests, the accelerated spread of insect pests in woodlands landscapes around the world has been of particular concern to forest owners and managers in recent decades.
In the face of such a scale of problems that affect our planet, there are programmes such as Copernicus, from the European Space Agency, which aims to complete an autonomous monitoring system, acting as the Earth’s doctor by monitoring the health of this aching patient in orbit. Through Copernicus’ six satellites, known as Sentinels, images of the Earth and its oceans, the atmosphere and climate change are collected for emergency response and security tasks.
Forests in the spotlight
Remote sensing technology is also used for daily applications in different sectors, such as analysing land cover to measure the impact of large-scale construction projects, surveying water status of rivers or even carrying out complex forest inventories.
In the case of forestry, LiDAR (Light Detection and Raging) remote sensing technology makes it possible to examine everything related to the forest accurately: from tree height and diameter, to the topography of forest land, to the volume of wood within a particular plot. LiDAR works by using airplanes or drones to fly over the desired study area and send light pulses to the ground, which are reflected by the ground or tree surface they encounter, and interpreted by sensors on the airplane or drone. This data, combined with other information collected by the vehicles, including GPS position, can be used to generate a geospatial image that allows foresters to measure a set of values within the terrain.
This technology, traditionally used for airspace research and meteorology, enables foresters to quickly access high-accuracy three-dimensional data and allows for a more informed, efficient forest management.
Looking for a needle in a haystack?
Forest management in Europe is a key pillar of a thriving bio-economy, providing about half of the EU’s renewable energy consumption and a wide range of ecosystem services. This important role means that, phenomena like damaging tree pests now represent not only a real threat to public health, but also to building a strong forest sector.
Tree pests can cause rapid and widespread damage to forests, reducing their value and economic prospects, and their role in mitigating climate change. Bark beetles, pine weevils, sawflies, budworms, nematodes and black arches are generally of little concern when they exist at non-harmful population levels, but when these species increase and behave in an invasive manner, concerns arise.
Due to a drastic increase in disease and insects across global forest biomass caused by warming in recent decades, sustainable management of forests to mitigate these destructive effects has become essential. Although conventional field measurement remains the most accurate way to quantify infestation stages, it entails a very costly and time-consuming process that does not solve the challenge of early detection. For this reason, remote sensing provides a more modern and accurate approach to provide explicit information with satellite and airborne Earth observation data.
In recent years the Earth observation data collected by this technology has increased enormously. The size and availability of the dataset at low cost facilitates a more systematic analysis of the impact of certain diseases or insects all around the globe.
Big Forest Data
The forestry sector is increasingly immersed in the era of Big Data, in which more and more researchers and technicians will be needed to efficiently and effectively analyse and manage the enormous amount of data acquired by EO and remote sensing.
Remote sensing can detect infected forests that show different symptoms at a distance more directly and easily. Depending on the type of damage, symptoms in trees may indicate decreased chlorophyll/water in foliage, leaf discoloration, defoliation or falls. Earth observation data obtained by satellite or airborne sensors captures the differences in radiation emitted by damaged trees versus healthy ones through different wavelength colours.
While progress in the acquisition and analysis of remote sensing data has significantly improved the feasibility of assessing forest disturbances such as pests, some challenges still exist:
- Early warning of forest damage: trees do not die instantly;
- Lack of a consistent monitoring of long-term recording of forest damage: new sensors, with increased capacity, lack historical data archives or have limited temporal and spatial coverage;
- Differentiation between forest disturbances: remote sensing has limited capacity to differentiate between forest damage caused by pests and any other natural or anthropogenic damage such as wildfires or logging.
Nevertheless, despite the challenges, there is also a wide range of opportunities. Remote sensing is emerging as an efficient, cost-effective and timely tool to help forest professionals anticipate problems and make more precise and sustainable decisions. European Union research initiatives such as My Sustainable Forest, which is co-funded by the H2020 programme, are a visible example of forestry’s great leaps in integrating this technology.
Seen as a revolutionary and crucial application by the sector and institutions, these projects aim to support sustainable forest management and offer advanced methods for more complete Earth observation data to assess the different stages of disease or insect invasion in different forest biomes in a more accurate way.
Sources & additional information
- Chen, G., & Meentemeyer, R. K. 2016. Remote sensing of forest damage by diseases and insects. Remote Sensing for Sustainability, 145-162.
- Beck, P. S., Zarco-Tejada, P., Strobl, P., & San Miguel, J. (2015). The feasibility of detecting trees affected by the Pine Wood Nematode using remote sensing. European Commission Joint Research Centre Institute for Environment and Sustainability.
- Wilschut, L. I., Heesterbeek, J. A., Begon, M., De Jong, S. M., Ageyev, V., Laudisoit, A., & Addink, E. A. 2018. Detecting plague-host abundance from space: Using a spectral vegetation index to identify occupancy of great gerbil burrows. International journal of applied earth observation and geoinformation, 64, 249-255.
