Water is the main limiting factor to life in the Mediterranean region, due to the intrinsic water constraints of the Mediterranean climate type: scarce annual precipitations, mainly concentrated in the cold months, with a more or less intense and long period of drought during summer.
Mediterranean terrestrial ecosystems (forests, woodlands, scrub and grasslands) form a landscape matrix supporting inland water systems, which may extend from upland mountainous areas to the coast. These ecosystems provide a wide range of goods and services, playing a critical role in water caption, retention, storage, and supply. Among the functions and benefits provided by forests in relation to water, we can mention:
- Flood mitigation effects: The soil of the upland forests stores rainfall water and regulates its flow towards lowland areas and the sea. Mediterranean forests and wetlands play a critical role in preventing and mitigating flood effects, which represent the most common and costly “water-related problem” in the region.
- Erosion and landslide control: Mature forests remove a considerable proportion of heavy rainfall events through evapotranspiration and their capacity to store and slowly release rainfall to groundwater aquifers, thus mitigating the possible negative effects of water runoff (sediment transport with soil erosion and risk of landslides).
- Groundwater recharge: Forest cover helps the slow transfer of exceeding water to groundwater aquifers, which release water even after periods of drought, providing a reliable source of water, essential for humans and the maintenance of ecosystem functions.
- Water purification: In principle, the forests soils and root systems help purify rainwater by absorbing contaminants. For this reason, maintaining and restoring forest soil not only plays an essential role in storing water, but also in maintaining the filter function and producing groundwater of high quality.
- Water flows: Forests and wetlands help to establish flow conditions that ensure life in aquatic and water-related ecosystems.
- Biodiversity: Well-preserved forests improve the environmental conditions of waterways (shading water systems and moderating water temperatures), and provide nutrients (i.e. leaves and decaying wood) to aquatic organisms. Moreover, forests create microclimate conditions around the waterways, which in the past have allowed the survival of very unique relic tertiary species populations during abrupt climate change events.
Effective strategies for climate change adaptation in the region will need to have the priority objective of securing the functions and benefits provided by the forests in relation to water, and securing the necessary water balance within ecosystems and between land uses. This will mean developing good soil management practices with innovative approaches to land uses, with a focus on species in agriculture and forestry.