Soil moisture deficit

Monitoring the pressure from soil moisture deficits can warn of potential impacts on plant development and soil health, supporting the assessment of drought-tolerant, resilient and vulnerable ecosystems. In 2000-2019, soil moisture in the growing season was several times below the long-term average in the EEA member countries plus the United Kingdom. The largest soil moisture deficits occurred in 2003, 2017 and 2019, affecting over 1.45 million km2 in 2019. Soil moisture content was also low in 2012, 2015 and 2018, contributing to increasingly frequent and intense drought pressure.

Published: ‒ 25min read

Soil moisture is essential for the development of plants. It regulates soil temperature, salinity, the availability of nutrients and the presence of toxic substances, and it gives structure to soil and contributes to preventing soil erosion. As soil moisture content is an important indicator of soil condition and the overall state of the land system, it determines land use suitability.

Droughts are relevant for several targets of the EU Biodiversity Strategy for 2030 related to protecting and restoring nature. As droughts hamper nature's ability to deliver a wide range of environmental, social, climate change adaptation and mitigation, and biodiversity benefits, they affect the implementation of the EU strategy on green infrastructure. Long-term objectives of the EU common agricultural policy (CAP) — viable food production, the sustainable management of natural resources, climate action and balanced territorial development — are also affected by droughts.

During the period 2000-2019, the growing season soil moisture content of the 38 EEA member countries (EEA-38) plus the United Kingdom was several times below the critical level. Soil moisture content exhibited a strong decreasing trend in the northern Continental region and hence drought pressure intensity increased in these areas. Other than in 2003, the largest soil moisture deficits occurred in the final 9 years of the period, indicating that drought pressure frequency is increasing. The area affected by growing season soil moisture deficits also increased between 2000 and 2019, increasing most in the last 3 years of the period. An increase of 80 % occurred, from an estimated 800 000 km2 in 2017 to 1.45 million km2 in 2019.

The 6 years with the lowest growing season soil moisture contents, covering the largest areas, were 2003, 2010, 2014, 2016, 2018 and 2019. The most intense drought pressures occurred in 2003, 2017 and 2019, with the most intense drought, affecting the largest area, occurring in 2019 (Figure 1). Soil moisture deficits were also severe in 2012, 2015 and 2018, with the area affected reaching an estimated 1.2 million km2 in 2018.

Although the Mediterranean region experienced frequent and intense drought events, it was the continental and Fennoscandia regions that experienced much lower than average soil moisture content between 2000 and 2019, with a trend towards worsening soil moisture deficits.

Between 2000 and 2019, the Baltic countries, Cyprus, Finland, Poland, Portugal and Sweden experienced significantly lower than average growing season soil moisture. Moreover, Cyprus, Czechia, Finland, Poland and Sweden showed strong decreasing trends and are therefore hotspots for potential impacts of drought. Belgium and the Netherlands did not have the lowest soil moisture deficits in the 27 EU Member States (EU-27) plus the United Kingdom, but decreasing trends indicate that conditions might become limiting for plant growth in the future.

These countries face increasing soil moisture pressures, potentially affecting sustainable food production on arable lands and the products and ecosystem services provided by forests.

Ireland and the United Kingdom were also among the countries with the lowest soil moisture deficits in the EU-27 and the UK, but increasing trends indicate that conditions might become more favourable for plant development. Austria, Bulgaria, Croatia, Greece and Romania showed improving soil moisture conditions during the 20-year period and, with the exception of Croatia, the long-term average soil moisture deficits were moderate in these countries.

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