You are here: Home / Database / Adaptation options / Water sensitive forest management
Original page

Adaptation option

Water sensitive forest management (2015)

It is increasingly recognized that both the availability and the quality of water are strongly influenced by forests and that water resources in many regions are under growing threat from overuse, misuse and pollution. The relationship between forests and water is therefore a critical issue that must be accorded high priority. Forest management measures can increase water yield, regulate water flow, and reduce drought stress for a forest. By intercepting precipitation, evaporating moisture from vegetative surfaces, transpiring soil moisture, capturing fog water and maintaining soil infiltration, forests influence the amount of water available from groundwater, surface watercourses and water bodies. By maintaining or improving soil infiltration and soil water storage capacity, they influence the timing of water delivery. By minimizing erosion, they minimize impairment of water quality due to sedimentation. Forests can also protect water bodies and watercourses by trapping sediments and pollutants from other upslope land uses and activities. In addition, along streams, forests provide shade, thus reducing water temperature.

The relationship between forests and water is complex and subject to myth and misinterpretation. Forests have been associated with improved water yields. As a general rule, however, in temperate climate conditions, forests consume more water than other land uses, increasing pressure on water resource security. In fact, an increasing number of studies have challenged the popular idea that more forests imply more and better water. To identify and correctly apply forest management to reduce water use is therefore a crucial aspect regarding water scarcity. Literature presents an equation to describe the water flow of a natural ecosystem: the water balance equation. The change in soil water storage for a given period is related to the amount of precipitations, rate of evapotranspiration (combination of the evaporation of the plants and the transpiration of the land surface to the atmosphere), surface runoff and deep drainage in a given period of time. The effects of forest management on the soil water storage are multiple and diverse. Measures that address existing forests include:

  • reduced density of stand stocking;
  • shorter length of the cutting cycles;
  • planting hardwood species;
  • regeneration from seedlings rather than sprouts;
  • afforestation.

This last measure, in particular near watercourses, brings benefits for the regulation of water flow and the maintenance of water quality, reducing the intensity of floods and the severity of droughts. Particularly relevant, in this context, are also practices such as harvesting, thinning and species mix choice. Canopy structure of mixed species plantations reduce transpiration, imposing less pressure on water if compared to mono-species plantations. By decreasing the number of trees in the stand, thinning may also be used to mitigate excessive forest water use. The positive impact of this measure may however be offset by increase water consumption due to increased growth of the remaining trees. Depending on the fraction of harvested land and on harvesting patterns, water yield usually increase after timber harvest. Different harvesting regimes may therefore impact differently on water resource security. Finally, shorter rotations decrease the period of time for which canopy is completely closed and may therefore also reduce water forest consumption. A relatively constant population of the stand by young trees may, however, counterbalance this effect. In addition, the use of fast growing species is usually more water intensive than slow growing species with higher rotations. While the use of forests has been increasingly advocated for a wide range of different objectives, the knowledge of the impacts of such programs on water scarcity still poses major research questions to the scientific community.

Additional Details
Reference information

Adaptation Details

Category
Green

Stakeholder participation

The implementation of this adaptation option requires the involvement of various actors (river managers, farmers, forest services, policy-makers, etc.) who should be involved to make the adoption of the adaptation option feasible.

Success and Limiting Factors

A key challenge for land, forest and water managers is maximizing the wide range of forest benefits without detriment to water resources and ecosystem function. To address this challenge, there is urgent need for better understanding of the interactions between forests/trees and water (particularly in watersheds), for awareness raising and capacity building in forest hydrology, and for embedding this knowledge and research findings in policies. There is also need to develop institutional mechanisms to enhance synergies in forests and water issues, and to implement and enforce national and regional action programmes.
Costs are a potential limitation of adapting management rules in silviculture to improve tree water balance. Afforestation is considered valuable given its benefits also under less pronounced climate change impacts. Need for more informed tree planting campaigns.

Costs and Benefits

Forests are serving multiple functions. Soil and water protection (and quality) also generally delivers biodiversity conservation, and vice versa.

The main issues determining the impact of afforestation on water are: (i) forest hydrology and related soil properties, (ii) benchmark landscape condition and (iii) water resources system configuration. If correctly designed, afforestation policies can alleviate negative effects and/or create additional benefits. One way consists in establishing new plantations on upper slopes. It reduces negative impacts on streamflow. Trees located in border of plantations have greater access to adjacent water; as a result the perimeter-to-area ratio may also be defined as to reduce forest water consumption. Finally, forest plantations are less nutrient and pesticide intensive than other land uses and may therefore consist in an instrument to grant higher quality water. Afforestation can also improve conditions for the sustainable livelihoods of local people. However, if not well managed or if established in places with high pollutant concentrations, afforestation may actually result in higher water acidification.

The Common Agricultural Policy (CAP) formulates rules and priorities to be pursued across sectors and rural areas. As forestry is the predominant land-use besides agriculture across Europe, the CAP also addresses forests and forestry issues. Many measures supported by the Rural Development Programme of CAPare directly linked to forestry protection and rehabilitation measures, including forest environment payments introduced for voluntary commitments to maintenance of water resources and water quality.

Via the Water Framework Directive also forestry services are affected. To support Member States in developing their Programme of Measures (PoMs), the European Commission financed a project compiling a catalogue of measures to tackle agriculture pollution, which also includes forestry related measures such as afforestation of agricultural land. Measures within the PoMs are directly linked with measures under axis 2 of the Rural Development Programme (RDPs) (described above), and other EU policies related to forest issues, such as EU Forestry Action Plan (FAP), Natura 2000 and the Biomass Action Plan (BAP).

Implementation Time

More than 25 years

Life Time

More than 25 years

Reference information

Websites:
Source:
DG ENV Prioject ClimWatAdapt

Keywords

Forest, management best practice, risk reduction, water

Sectors

Biodiversity, Disaster Risk Reduction, Forestry, Water management

Climate impacts

Droughts, Flooding, Storms, Water Scarcity

Governance level

Sub National Regions

Geographic characterisation

Global

Document Actions