Satellite data for Germany's forests in distress

EO Wald's open-access interactive maps help the timber industry, local authorities and policymakers respond swiftly to events and manage reforestation. The goal is to enable economical and sustainable forest development, particularly in response to our changing global environment. Serving as Earth's green lungs, healthy forests absorb large amounts of carbon and are more resilient to extreme climate events.

Recent years have seen unusually intense droughts, heatwaves and storms take their toll on Germany's forests. Stressed trees are also more vulnerable to pests, leading to widespread die-off in many places – in some cases, large swathes of trees must be felled as a protective measure. With easily understandable maps, EO Wald offers unique insights into these developments. The new data portal was developed at the DLR Earth Observation Center (EOC) and validated within the ForstEO project.

EO Wald offers views and comparisons at state, district, municipal and pixel levels. For areas selected, a timeline shows the month-by-month percentage loss of canopy cover. Users can also adjust the time periods or look at certain areas in a monthly, seasonal or annual overview. Thanks to the high spatial and temporal resolution, users can see on the maps when and where losses occurred, which helps to better identify the causes. For example, losses that spread in a circular pattern are indicative of pests, whereas geometric areas hint at logging. Precise timings allow users to pinpoint specific events, such as wildfires, storms or intentional clearing.

Satellite images captured in winter reveal the majority of losses: it is during the cold months when timber tends to be harvested, including the removal of damaged or diseased trees. Winter timber is of good quality, and the frozen forest floor is less easily damaged by heavy machinery. Winter storms also lead to hefty losses as they can hit large areas and damage healthy trees. Satellite-based remote sensing and ongoing monitoring efforts are vital to tracking and understanding such developments.

Big data for practical use

DLR is Germany's leading institution in big-data analysis of large-scale Earth observation data and converting it into a wide range of useful information products. To determine canopy loss, its researchers used data from many sources, including the European Copernicus programme's Sentinel-2 satellites and the US Landsat-8 and Landsat-9 satellites.

"EO Wald takes us on a scientific journey through time, so to speak,” explains project manager Frank Thonfeld, of the EOC. “For the time frame under investigation, from 2017 to 2024, we have analysed tens of thousands of monthly datasets and made them publicly accessible. I am particularly pleased that we are already in dialogue with authorities and initial users." Indeed, the EO Wald dataset is already being used by the Bavarian State Forest Enterprise (Bayerische Staatsforsten AöR) and the Bavarian State Institute of Forestry forestry (Bayerische Landesanstalt für Wald und Forstwirtschaft).

Human and environmental impact

Extreme weather events such as unusually intense periods of drought and heatwaves are expected to increase with global climate change. The health of spruce forests, dominant in Germany, is a case in point – having already suffered dramatic losses due to dry heat, which encourages bark beetles – a trend that is likely to continue in the coming years. In terms of forest management, it is therefore crucial to anticipate such developments. Satellite data time series covering multiple years make it possible to continuously observe large areas of forest and detect changes.

This applies just as much to natural processes as it does to planned and unplanned human intervention. Due to forest damage in recent years, logging over exceptionally large areas has proven necessary, for instance. Such losses impact the entire forest ecosystem and influence microclimates, water balance, surface runoff, groundwater formation, water quality and biodiversity. What's more, the impacts of climate change also need to be quantified in greater detail. EO Wald now equips decision-makers with a scientific data foundation to devise suitable strategies for the protection and expansion of forests.

Reforestation with a vision

When it comes to forest reconstruction and reforestation, foresight is key: which species of tree can withstand current climate conditions – and will they cope with the conditions prevailing 60 to 80 years from now? After World War II, spruce trees – many of them non-native – were replanted as the primary provider of timber. Given their similar age and growth structure, they are not very resilient as a monoculture.

Current data clearly shows that pure plantations of spruce, pine and beech trees are particularly vulnerable, while mixed woodlands are more resilient and distribute risk more effectively. Biodiversity and a mixed forest structure featuring both young and old trees are therefore key to healthy forests. As it can take years, if not decades, for a new forest to form, developing a woodland for economic use presents a huge challenge.

To help overcome such challenges, DLR's new data platform provides a clear overview of canopy losses. Regrowth potential is not yet included, as young plants are still too small to be detected during the seven-year period of observation. High-resolution Earth observation satellites such as Sentinel-1 and Sentinel-2 do, however, continuously capture the condition of the forests. Researchers at DLR’s EOC are therefore already working on new datasets and plan to further expand the online service. With EO Wald, DLR contributes its extensive remote-sensing expertise to support sustainable forest management and restoration.

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