After the dry early summer, the forest canopy condition reached a negative record beginning of July but largely improved until end of July due to wetter conditions.
Beginning of July, the Forest Condition Monitor showed a stark increase in lowest quantiles, likely as a result of ongoing drought in that period. It’ll be interesting to analyze canopy changes in July after repeated rainfall ended the drought.
In mid June, forest canopy greenness declined in many parts of Germany due to emerging drought conditions. In particular, the Thüringer Wald, the Schwarzwald, the Eifel, and the majority of Bavaria and Baden-Württemberg were characterized by low canopy greenness forest condition
The late phenology as observed over the cool and wet spring period seems to catch in May as indicated by a reduction of low quantiles. Studying the development of ForestCondition 2023 over the next weeks will be interesting due to increasingly drier conditions.
The Forest Condition Monitor season 2023 has started with relatively low quantiles in several parts of Germany. However, this might be caused by the relatively cool and moist spring conditions, which have delayed phenology and the onset of the growing season.
After a record summer with respect to canopy greenness decline, the situation is slowly improving, yet extreme.
The recent development of the Forest Condition Monitor (current state July 4th) indicates a thrice as large area (in total 18,000 km² corresponding to roughly 1/6 of forest area in Germany) to feature lowest quantiles in comparison to same period in 2018. Moreover, it now seems that in contrast to earlier in the season of 2022 (forests in southern Germany were less affected) drought-effects are observed everywhere. Since the drought severity increased since July 4th, it seems likely that the situation will worsen.
The German Forest Condition Monitor has experienced a major revision. It is now possible to interactively select dates and municipal districts within Germany to visualize NDVI quantiles in conjunction with Sentinel2 optical imagery. The new app can be found at: deutschland.waldzustandsmonitor.de
2021 featured a diverse season with a late season start while the overshoot precipitation in spring and summer led to a relaxation of the drought-stress since 2018 (high greenness in many parts of German forests).
Peak season (end of July) NDVI indicates a heterogeneous pattern across Europe. While parts of Central Europe featured a relaxation of the drought of the previous three years due to extensive precipitation, parts of Scandinavia featured low quantiles, possibly due to a relatively warm and dry summer. At the same, parts of the Mediterranean (in particular Italy, Balkan) also featured relatively low NDVI values, reflecting the extraordinary heatwaves of summer 2021 which negatively affected forests.
After the summer break, the forest condition monitor displays a relaxation from the drought of the past three years over large parts of Germany. However, hotspots of forest dieback such as the Harz or Thüringer Wald are yet characterized by very low quantiles and proportions. And despite the relaxation, the drought 2018-2020 has had a significant impact on German and Central European forests as also indicated in the quantiles and proportions of those years.
The greenness of German Forests has in the meantime reached normal to above average values, probably due to a relaxation of the drought in the past three years in course of precipitation surplus and a recovery from the delayed phenology in the extraordinarily cool spring 2021. However, forests in Brandenburg, the Harz and Northrhine-Westphalia yet seem to suffer from drought legacies (NRW) and/or ongoing drought (Harz, BB) in these regions.
The hypothesis from July 1st that high precipitation in spring relaxes the drought situation is supported by increasing shares of high quantiles (blue colors) in the recent update. However, some hotspots of potential forest decline remain in Central Germany (i.e. Northrhine-Westfalia, Hessen, and Brandenburg) matching some of the remaining drought hot-spots early in June 21 as indicated by the German Drought monitor. The development for these remaining hot-spots of forest decline over the next weeks will be particularly interesting.
The high share of lowest quantiles and low proportions has partly decreased in course of spring greening, supporting the interpretation from June 20th that the low greenness early in spring was caused by a delayed phenology. The development over the next weeks will be particularly interesting since large parts of Germany have received plenty precipitation thereby potentially dampening the soil drought and relaxing the drought-stress of trees.
Large parts of German forests feature extraordinarily low greenness which likely is a combined result of drought legacies from 2018-2020 but also caused by the delayed spring phenology in course of the coldest spring since 1983 (see also these links for temperature anomalies and phenology anomalies).