OBSERVER: CLMS releases HR-VPP product to assess ecosystems and biodiversity

Thu, 02/09/2021 - 12:00

Copernicus Land Monitoring Service (CLMS) data play an important role in the monitoring and management of the growing demands for more ambitious environmental targets across Europe. In the first European ecosystem assessment report The European Commission’s Executive Vice-President in charge of the EU Green Deal and Climate Action, Frans Timmermans said: “A healthy, thriving and resilient nature is at the core of our lifestyles, thriving economies and resilient societies. Europe’s ecosystems - from forests, rivers and lakes to farmland, urban green spaces and soils – form a safety net that protects us from extreme climate impacts and provides us with essential services, vital for our physical and mental health. However, Europe’s ecosystems are under increasing pressure, suffering from the impact of climate change and land use intensification”.

The new CLMS High Resolution Vegetation Phenology and Productivity (HR-VPP) product has been launched on 2 September 2021. It covers the years 2017-2020, and will be updated yearly from 2022 onwards. This high spatial and temporal resolution land monitoring dataset will allow a better monitoring of vegetation dynamics and allow the assessment of climatic, as well as anthropogenic impacts on ecosystems. With its wide range of applications, the HR-VPP product increases the ability of CLMS to support the implementation of key EU policies , such as the Biodiversity Strategy 2030, the Common Agricultural Policy (CAP), and climate initiatives such as the LULUCF regulation for 2021-2030, the Urban Agenda, the Circular Economy policies of the EU, as well as the UN Sustainable Development Goals.

Phenology as key bio-indicator of ecosystems

Phenology is one of the key components of life on Earth, describing the ability of living organisms to adapt to environmental resources, and relating to growth and reproduction. Plant phenology is among the most important species traits, describing seasonal events such as leaf emergence, bud burst, leaf unfolding, flowering, and leaf senescence. Birds time their nesting so that eggs hatch when insects are available to feed nestlings, and insects’ emergence is often synchronised with leaf out in host plants. Phenology also determines migration patterns of fauna in order for it to exploit favourable climatic conditions, or to avoid unfavourable ones.

Earlier flowering also poses health issues to people affected by allergies. Farmers and gardeners need to know the schedule of plant and insect development to decide when to apply fertilizers and pesticide and when to plant to avoid frosts. Phenology influences the abundance and distribution of organisms, ecosystem services, food webs and global cycles of water and carbon. In summary, phenology provides an integrated measure of ecosystem responses to climatic factors as well as to human induced disturbances, and hence, has a strong potential to monitor the condition and degradation of ecosystems.

Figure 1: Illustration of leaf phenology stages typically observed in the growing cycle

Vegetation dynamics observed from space

Vegetation phenology addresses periodic plant life-cycle events such as emergence, flowering and bud-burst (in spring) and leaf coloration and fall (in autumn). These events can be observed in the field, but typically only at the individual plant, species, or plot level. At larger scales, we can rely on time series of satellite-based vegetation indices. These indices, typically derived from optical satellite imagery such as that provided by the Copernicus Sentinel 2, assess the vigour of green biomass and allow the differentiation of the intensity of photosynthetic activity. This in turn depends on the plant functional types and vegetation dynamics during the growing season.

Figure 2: Seasonal variability in vegetation index across an agricultural landscape in Landen, Belgium

Within the wide spectra of vegetation indices, the PPI (Plant Phenology Index, developed at Lund University by Hongxiao Jin and Lars Eklundh) is specifically designed to optimise an efficient monitoring of vegetation phenology. That is why it was selected in the HR-VPP service as the key component to study vegetation dynamics. How this is done at the pixel level is illustrated in Figure 3. Each Sentinel-2 observation is first converted in a PPI value (grey dots). Next, all observations contaminated by clouds and shadows are disregarded (partly filled grey dots). The resulting irregular time series of high-quality observation are then transformed into a smooth continuous curve (red curve), highlighting the seasonal dynamics. At this point, phenological metrics such as the start (a), maximum (e) and end (b) of season can be derived.

Figure 3: Smooth seasonal trajectory (red line) fitted to Sentinel-2 PPI observations (grey dots). Letters denote different phenological parameters that are output as data layers in HR-VPP

HR-VPP product has been released today

Derived from Sentinel-2 and covering a pan-European scale, these high-resolution vegetation phenological and productivity parameters capture the spatial patterns of vegetation dynamics repetitively over vast areas at 10 m spatial resolution. The pan-European High-Resolution Vegetation Phenology and Productivity products suite (HR-VPP) has been released today. The datasets are provided at a high level of spatial detail (10 m x 10 m), derived from data supplied by the Copernicus Sentinel-2 satellite constellation (Sentinel-2A and Sentinel-2B). They are generated over the entire EEA39 region (33 Member States and 6 cooperating countries) for the period January 1, 2017, onwards, with yearly updates from 2022 onwards.

Figure 4: False Colour Composite made up from three phenology parameters, illustrating variability across a landscape around Lago di Mezzola, Italy

The product suite consists of three product categories:

First, four different Vegetation Indices (VI) record the status of the vegetation for every 10m pixel within 12 hours after observation. These data sets target experts due to their irregular time-interval and to the very large amount of data they contain.
Second, the Seasonal Trajectories (ST), like the vegetation indices, show the status of the vegetation, but at a regular time-interval of 10 days, with any gaps in the observations due to clouds or other factors is being filled. These data sets target novice users, able to deal with time-series data.
The third and final product in the suite is the Phenological and Productivity Parameters (VPP) data set. It provides metrics at yearly intervals for up to two growing seasons, i.e., start of the season, end of season, seasonal productivity, etc. (Figure 1) and targets novice users.

Eva Ivits, Technical Officer at EEA, responsible for HR-VPP product suite says: “The new HR-VPP product of the Copernicus Land Monitoring service will facilitate a more detailed and frequent assessment of vegetation responses to disturbances with higher spatial resolution than previously available. Due to the semi-automatic processing flow, production will be accelerated thus enabling us to derive timely indicators on climatic and anthropogenic impacts on the ecosystems.”

Continuous stream of information

The continuous stream of daily Vegetation Indices provides an update of the vegetation status across the European continent every 5 days and will enable us to continuously monitor the ecosystems health with a high level of detail. This stream of data is turned into yearly maps to support quick assessments for all ecosystem types (forest, grassland, etc.).

Bruno Smets, Project Manager at VITO, who is leading the consortium producing the HR-VPP product for the EEA and Copernicus says: “We are confident that this new product will bring an entire new insight into the monitoring, analysis and frequency of reporting duties of Member States, and will also support decision makers in their policy implementation activities. In the upcoming year we will add a number of tools to further ease such analysis.”

You can access this new product at: https://land.copernicus.eu/pan-european/biophysical-parameters/high-resolution-vegetation-phenology-and-productivity.

The product is representative of the ground-truth, having undergone a full calibration campaign using in situ ground data from phenological cameras and carbon flux towers, and manual ground observations of phenology and agricultural events. Lars Eklundh, Professor at Lund University, who is responsible for the scientific component of the HR-VPP product says: “Monitoring phenology over the entire European continent is a challenge but, by using a broad set of reference data and engaging a suite of topical experts in the calibration and validation of HR-VPP, we are confident that the product will prove its value both to operational users and the scientific community”.

Further reading and data access

Are you interested to read more about the HR-VPP products? Then head over to the Copernicus Land Monitoring Service web site.

The HR-VPP products are firstly made available on WEkEO, one of the Copernicus Data and Information Access Services (DIAS). So make sure to visit the WEkEO data portal.