The indicator addresses anomalies and long term trends of vegetation productivity derived from remote sensing observed time series of vegetation indices in areas that are pressured by drought.
Drought pressure is computed using the Soil Moisture Anomaly (SMA) time series of the European Drought Observatory of the Joint Research Centre:
Drought impact is indicated as a severe negative annual productivity anomaly under drought pressured areas, i.e. under negative annual soil moisture anomaly. Detailed indicator specifications are presented under Methodology.
Annual drought pressure is derived at the pixel level and is simply defined as:
SMA(gs) < -1, eq 1
where SMA(gs) is the long term (2000-2019) annual soil moisture anomalies aggregated (averaged) within the vegetation growing season.
Negative soil moisture anomalies indicate that the annual average availability of soil moisture to plants drops to such a level that it has the potential to affect terrestrial vegetation and, hence, cause persistent changes in ecosystem condition.
In indicating drought pressure, strong negative soil moisture anomalies are used withsetting a threshold at -1 standard deviation. This is to allow the monitoring of vegetation response to considerable soil moisture deficit values. By doing so impacts can be easier distinguished from fluctuating vegetation anomalies.
The threshold -1 was selected to indicate drought pressure following the recommendations of the EC Joint Research Centre (https://edo.jrc.ec.europa.eu/documents/factsheets/factsheet_soilmoisture.pdf ). This approach is also followed by the EEA indicator addressing soil moisture deficit (https://www.eea.europa.eu/data-and-maps/indicators/soil-moisture-deficit) .
Annual drought impact is quantified as:
SMA(gs) < 0 AND LINTa <-0.5, eq2
where LINTa (Large INTegral anomaly) is the long term (2000-2019) annual anomalies of remote sensing derived growing season productivity approximated by vegetation indices (see more explanation below).
The LINT anomalies were calculated as standard deviations from the loing term mean, i.e.
LINTa (year xi-n) = (LINT (xi)-Lint (avr))/(LINT (xi)-LINT(std)), eq. 3
The threshold of -0.5 standardised deviation was selected such that it indicates small deviations from the long term mean to allow for moderate productivity levels under drought impact to be accounted for. In a continental wide study this is a prgamatic solution that allows a wide overview of drought impact situations in Europe. However, local studies might consider setting a lower/higher threshoild reflecting local conditions.
The LINT is calculated as in the relatied vegetation productivity indicator:
https://www.eea.europa.eu/data-and-maps/indicators/land-productivity-dynamics/assessment (see sections on indicator definition and methodology).
Vegetation productivity is derived from remote sensing observed time series of vegetation indices. The vegetation index used in the indicator is the Plant Phenology Index (PPI, Jin and Eklundh, 2014). PPI is based on the MODIS Nadir BRDF-Adjusted Reflectance product (MODIS MCD43 NBAR. The product provides reflectance data for the MODIS “land” bands (1 - 7) adjusted using a bi-directional reflectance distribution function. This function models values as if they were collected from a nadir-view to remove so called cross-track illumination effects. The Plant Phenology Index (PPI) is a new vegetation index optimized for efficient monitoring of vegetation phenology. It is derived from radiative transfer solution using reflectance in visible-red (RED) and near-infrared (NIR) spectral domains. PPI is defined to have a linear relationship to the canopy green leaf area index (LAI) and its temporal pattern is strongly similar to the temporal pattern of gross primary productivity (GPP) estimated by flux towers at ground reference stations. PPI is less affected by presence of snow compared to commonly used vegetation indices such as Normalized Difference Vegetation Index (NDVI) or Enhanced Vegetation Index (EVI).
The product is distributed with 500 m pixel size (MODIS Sinusoidal Grid) with 8-days compositing period. The Large integral is the mathemtaical integral calculation of the smoothed and gap filled PPI time series between the start and end of the season points on the curve.
All input datasets are derived with a wall-to-wall coverage of the land surface.
No gap filling was needed.
Justification for indicator selection
Drought is a recurring and extreme climate event that is induced by a temporary water deficit and may be related to a lack of precipitation, soil moisture, streamflow, or any combination of the three taking place at the same time. Drought differs from other extreme natural events in several ways. First, unlike earthquakes, floods or tsunamis that occur along generally well-defined fault lines, river valleys or coastlines, drought can occur anywhere (with the exception of desert regions where it does not have meaning). Secondly, drought develops slowly, resulting from a prolonged period (from months to years) of water supply conditions that are below the average at a specific location.
Because of their long-lasting socioeconomic impacts, droughts are by far considered the most damaging of natural disasters . The immediate impacts of short-term droughts (i.e. a few weeks duration) are, for example, a fall in crop production, poor pasture growth and a decline in fodder supplies from crop residues. Prolonged water shortages (e.g. of several months or years duration) may, among others, lead to a reduction on hydro-electrical production and potentially increase wildfire occurrences on land-based natural and managed ecosystems.
Although droughts are typically associated with aridity, they can occur in most parts of the world, even in wet and humid regions, and can profoundly impact agriculture, basic household welfare, tourism, ecosystems and the services they provide. For example, in arid and semi-arid ecosystems (including the Mediterranean regions), limiting water availability is a recurrent phenomenon and governs plant growth and phenology. On the other hand, in temperate, boreal and tropical ecosystems, sporadic prolonged dry periods can lead to water-limited conditions and can have far-reaching impacts on ecosystem carbon (C) balance and structure.
The monitoring and assessment of drought impacts is complex because different types of impacts vary in their intensity, often in different phases of the given drought event, as indicated above. Therefore, most empirical studies of drought impacts have focused on agricultural crop production, which is direct, immediately observable, well understood, and easy to quantify (Wilhite, 2000). Reports about drought impacts in the category 'terrestrial ecosystems' were only found for a few years and are limited in number in the EDII database (Stahl et al., 2016). This agrees with the earlier conclusions of Lackstrom et al., which claim that there is a lack of data and understanding of drought impacts on sectors other than agriculture and water resources.
Differences in the physiological response of vegetation to water deficits determine different levels of sensitivity and resilience of terrestrial ecosystems to drought, and ultimately influence the type of drought impacts, i.e. differentiating those impacts that slow growth or reduce greenness, those that lead to loss of biomass, and those that result in plant mortality. Consequently, significant changes in the amount of vegetation productivity provide an indication/early warning of imminent irreversible impacts in ecosystems' equilibrium states.
In May 2020, the EU adopted a Biodiversity Strategy to 2030, related to protecting and restoring nature. The strategy states that the ‘biodiversity crisis and the climate crisis are intrinsically linked. Climate change accelerates the destruction of the natural world through droughts, flooding and wildfires, while the loss and unsustainable use of nature are in turn key drivers of climate change’. Droughts are negatively affecting agricultural ecosystems and food security, the resilience of forest ecosystems and the ability of green urban spaces to protect people against heat waves. In particular, the impacts of extended droughts on ecosystems need to be assessed because they can lead to significant loss of vegetation productivity and irreversible damage to the condition of ecosystems and can lead to land degradation.
For the EU, the cost of not reaching the 2020 biodiversity headline target of halting the loss of biodiversity and ecosystem services has been estimated at 50 billion EUR per year . In addition, to undermining these economic benefits, loss of biodiversity means that ecosystems and societies that rely upon them are more fragile and less resilient in the face of challenges such as climate change, pollution and habitat destruction. Droughts have an impact on several land and soil functions, as well as ecosystem services, both in urban and rural areas. For example, droughts have an impact on water resources available for human use in agriculture, cause habitat loss, migration of local species and their replacement by alien ones in open rural systems, and consequently soil erosion and biodiversity degradation. By pressuring natural ecosystems, droughts hamper the achievement of EU Biodiversity 2020 objectives.
Drought pressure on natural ecosystems has also an important role on the implementation of the EU Strategy on Green Infrastructure (GI). In contrast to the most common ‘grey’ (man-made, constructed) infrastructure approaches that serve one single objective, GI promotes multifunctionality, which means that the same area of land is able to perform several functions and offer multiple benefits if its ecosystems are in a healthy state. More specifically, GI aims to enhance nature's ability to deliver multiple valuable ecosystem goods and services, potentially providing a wide range of environmental, social, climate change adaptation and mitigation, and biodiversity benefits. Drought diminishes the normal condition of ecosystems and their capacity to provide services that could be integrated in green infrastructures.
Under EU legislation adopted in May 2018, EU Member States have to ensure that greenhouse gas emissions from land use, land use change and forestry (LULUCF) are offset by at least an equivalent removal of CO₂ from the atmosphere in the period 2021 to 2030. Ultimately, the capacity of forests and soils on a given area of land to remove carbon from the atmosphere will depend on a number of natural (regional/geographical) circumstances such as variations in growing conditions (temperature, precipitation and droughts) and natural disturbances (storms, fires) as well as past and present management practices (e.g. rotation lengths which affect the distribution of age classes in forest stands). By measuring changes in emissions and removals relative to business-as-usual projections, these circumstances (such as drought pressure) will be "factored out" so that only changes related directly human-induced activities are measured. This also provides incentives for improving on the current situation and gives an equal value to mitigation whether through sequestration or conservation or material and energy substitution.
The role of the CAP is to provide a policy framework that supports and encourages producers to address economic, environmental (i.e. relating to resource efficiency, soil and water quality and threats to habitats and biodiversity) and territorial challenges, while remaining coherent with other EU policies. This translates into three long-term CAP objectives: viable food production, sustainable management of natural resources and climate action and balanced territorial development. Given the pressure of drought on natural resources, agriculture has to improve its environmental performance through more sustainable production methods. Farmers have also to adapt to challenges stemming from changes to the climate by pursuing climate change mitigation and adaption actions (e.g. by developing greater resilience to
No specific targets.
Related policy documents
- Climate-ADAPT: Adaptation in EU policy sectors. Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored.
- Climate-ADAPT: Country profiles. Overview of activities of EEA member countries in preparing, developing and implementing adaptation strategies.
- Decision No 1386/2013/EU of the European Parliament and of the Council of 20 November 2013 on a General Union Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. Published: 2013-11-20 Corporate author(s): Council of the European Union, European Parliament Subject: biodiversity , economic growth, environmental impact , environmental protection, EU programme, investment , management of resources , pollution control.
- EU 2020 Biodiversity Strategy. In the Communication: Our life insurance, our natural capital: an EU biodiversity strategy to 2020 (COM(2011) 244) the European Commission has adopted a new strategy to halt the loss of biodiversity and ecosystem services in the EU by 2020. There are six main targets, and 20 actions to help Europe reach its goal. The six targets cover: full implementation of EU nature legislation to protect biodiversity; better protection for ecosystems, and more use of green infrastructure; more sustainable agriculture and forestry; better management of fish stocks; tighter controls on invasive alien species; a bigger EU contribution to averting global biodiversity loss.
- EU Adaptation Strategy Package. In April 2013, the European Commission adopted an EU strategy on adaptation to climate change, which has been welcomed by the EU Member States. The strategy aims to make Europe more climate-resilient. By taking a coherent approach and providing for improved coordination, it enhances the preparedness and capacity of all governance levels to respond to the impacts of climate change.
- EU Biodiversity Strategy for 2030. The European Commission has adopted the new EU Biodiversity Strategy for 2030 and an associated Action Plan (annex) - a comprehensive, ambitious, long-term plan for protecting nature and reversing the degradation of ecosystems. It aims to put Europe's biodiversity on a path to recovery by 2030 with benefits for people, the climate and the planet. It aims to build our societies’ resilience to future threats such as climate change impacts, forest fires, food insecurity or disease outbreaks, including by protecting wildlife and fighting illegal wildlife trade. A core part of the European Green Deal, the Biodiversity Strategy will also support a green recovery following the COVID-19 pandemic.
- Evaluation of the EU Adaptation Strategy Package. In November 2018, the EC published an evaluation of the EU Adaptation Strategy. The evaluation package comprises a Report on the implementation of the EU Strategy on adaptation to climate change (COM(2018)738), the Evaluation of the EU Strategy on adaptation to climate change (SWD(2018)461), and the Adaptation preparedness scoreboard Country fiches (SWD(2018)460). The evaluation found that the EU Adaptation Strategy has been a reference point to prepare Europe for the climate impacts to come, at all levels. It emphasized that EU policy must seek to create synergies between climate change adaptation, disaster risk reduction efforts and sustainable development to avoid future damage and provide for long-term economic and social welfare in Europe and in partner countries. The evaluation also suggests areas where more work needs to be done to prepare vulnerable regions and sectors.
- Green Infrastructure (GI) — Enhancing Europe’s Natural Capital. Green infrastructure is a strategically planned network of natural and semi-natural areas with other environmental features designed and managed to deliver a wide range of ecosystem services such as water purification, air quality, space for recreation and climate mitigation and adaptation. This network of green (land) and blue (water) spaces can improve environmental conditions and therefore citizens' health and quality of life. It also supports a green economy, creates job opportunities and enhances biodiversity. The Natura 2000 network constitutes the backbone of the EU green infrastructure.
- Our life insurance, our natural capital: an EU biodiversity strategy to 2020. European Commission (2011).
- Science for Environment Policy. In Depth Report – Ecosystems Services and Biodiversity. European Commission 2015.
The approach cannot account for land use/land cover changes that have occurred within a pixel for the period of analysis. For example, clear cuts within forest ecosystems or the use of irrigation systems as part of the management in agricultural areas might increase or decrease the vegetation productivity independently of drought occurrences. This can introduce noise in the datasets that might bias the pixel-based relationships between drought pressure and vegetation productivity.
Another source of uncertainty is related with the simplification of the drought impact model for its implementation in the operational setting. In this study, only meteorological drought distribution and intensity is considered. Still, in some cases, the start, end, severity, and spatial extent of a drought, as well as the propagation of its impacts through the whole land systems might be changing due to additional climate and/or surrounding biophysical conditions, such temperature, snowpack, albedo and soil water holding capacity.
Data sets uncertainty
The dataset represents the average trend of productivity of all terrestrial ecosystems within an area covered by a pixel of 500x500m. Therefore, the dataset can only be used at the ecosystem level indicating drought impacts on main terrestrial ecosystems. As opposed to field measurements, remote sensing products measure vegetation light absorption from a satellite at several hundred km height which might introduce bias due to atmospheric disturbances.
No uncertainty has been identified.