Wind damage has long been one of the primary challenges in forestry, with its impact varying depending on the type of forest affected. For the past 75 years, windstorms have been the most damaging forest disturbance in planted and managed forests in the UK and across continental Europe, causing disruption and economic loss, affecting livelihoods and communities, and impacting infrastructure including transport, electricity, and communication.

Forest Research have released a new video about the increasing risks of wind and storms and ways to mitigate their damage, including by using the wind risk model and decision support system, ForestGALES.

The increasing risk from strong winds and storms

Projections point to an increase in the frequency and intensity of extreme wind speeds and the number of storms over the coming years. The vulnerability of trees to wind damage is compounded by other factors such as increased rainfall, which under certain conditions can affect tree anchorage on poorly draining soils, and other climatic and biotic stressors (e.g. prolonged intense droughts and attacks from pests and diseases) that can impact trees’ vigour and their mechanical integrity.

Often the main consequence of windthrow is economic damage as it can lead to significant timber loss and severely limit the longevity of carbon stocks registered under accreditation schemes such as the Woodland Carbon Code. Indirect economic losses after windthrow events can be substantial. For example, operations to assess and address the impact of a storm, as well as clearing affected areas and when possible salvaging timber can be time-consuming and in the case of leaning trees potentially dangerous.

Building resilience

Forest managers can improve forest resilience to windstorms through a variety of measures including:

• Forest diversification: Use a variety of species and age structures to help forests better withstand windstorms rather than relying on monocultures and even-aged stands.
• Continuous cover forestry: Continuous cover forestry might reduce the risk of entire stands being blown down while often allowing existing younger trees and natural regeneration to fill in gaps quickly after a storm, promoting long-term resilience and faster recovery.
• Thinning operations: The risk of wind damage always increases after thinning, as more wind is allowed to enter a stand, exposing the retained trees to higher forces than those they had been exposed to during their previous development. When feasible, and depending on local conditions, early thinning interventions might promote the development of more favourable tree tapers and root systems, setting forest stands on trajectories of growth and development that are less vulnerable to windblow.

Predicting and managing wind risk

ForestGALES, a wind risk model and decision support system developed by Forest Research, helps managers assess the vulnerability of their forests and the likelihood of storm damage and plan interventions accordingly.

The model calculates the vulnerability and risk of forest stands and individual trees to wind damage – for both stem breakage and tree uprooting – allowing users to explore scenarios of different silvicultural interventions and the impact of climate change on stand development.

ForestGALES is the industry-standard wind risk tool in the forestry sector in the UK and forms an important part of forest management decision support systems in several other countries in Europe and further afield. It is validated to use across a range of species and can be used under a range of conditions.

Read more at Windthrow – Forest Research