Adapting to Climate Change: The Alice Holt ‘Living Laboratory’ Forest

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Summary

Alice Holt Forest in Hampshire is a demonstration site for climate change adaptation in woodlands typical of southeast England. Three areas have been established to trial measures such as underplanting drought-tolerant species, thinning pines to reduce competition for water, and testing tree provenances from warmer climates. These interventions address projected risks of hotter, drier summers and more frequent droughts, which threaten tree health, biodiversity, and forest functions. Monitoring of growth, soil moisture, and visitor feedback informs learning, while a self-guided adaptation trail showcases the work. The project aims to build resilience, share lessons with the wider forestry sector, and move woodland management away from “business-as-usual” towards proactive adaptation.

Key Messages

• From theory to practice: The project moves beyond academic research to create real-world, on-the-ground examples of adaptation that other foresters can visit and learn from.
• Diversification builds resilience: The core of the strategy involves increasing diversity in tree species, age structure, and genetic origin (provenance) to buffer the forest against uncertain future climate conditions.
• Proactive management is essential: The initiative directly tackles the main climate threat for southeast England—drought—by testing practical management techniques like thinning stands to reduce competition for water.
• Sharing knowledge is a primary goal: A key objective is to use the demonstration areas to share learning, build confidence, and encourage the wider forestry sector to implement adaptive management practices.

A key adaptation technique used at Alice Holt Forest is underplanting, where new, more resilient tree species like beech are planted beneath an existing canopy of mature Corsican pine. This increases species and age diversity, creating a more complex and robust forest ecosystem for the future.

Background

Alice Holt Forest is in northeast Hampshire (southeast England) and is managed by Forestry England. An ancient woodland complex, the forest covers more than 850 ha, and comprises both plantation on ancient woodland sites and ancient semi-natural woodland. Much of the forest has been selected as being of county/regional significance for its biodiversity interest as a Local Wildlife Site/Site of Importance for Nature Conservation. The mix of broadleaf tree species and coniferous woodland provide many benefits for the local community, the environment and for the forestry sector. The forest receives more than 650000 day visitors each year. The work undertaken at Alice Holt Research Station is of international importance and is the site of historic research trials dating back to 1943. It is therefore essential to retain a healthy and productive forest for the changing climate.

Three priority challenges addressed at Alice Holt

The project was designed to tackle key vulnerabilities in temperate forests. The three demonstration areas each address a different type of challenge common in woodland management.

1. The challenge of monoculture vulnerability

This represents the risk inherent in relying on stands of a single species, which can be highly susceptible to new pests, diseases, and climate stressors like drought. The first demonstration area addresses this directly in a mature stand of Corsican pine.

• Action: Researchers and foresters have underplanted the mature pine with a mix of other species, including hornbeam (chosen for its higher drought tolerance) and beech.
• Outcome: This action breaks up the monoculture, introducing greater species and age diversity. It creates a more resilient, multi-layered forest better prepared for the eventual decline of the Corsican pine and future climate stress.

2. The challenge of increased drought stress

With summers projected to become hotter and drier, trees will face intense competition for limited water resources. The second demonstration area tests a direct management intervention to mitigate this threat.

• Action: A stand of young Corsican pine has been thinned to two different intensities.
• Outcome: The hypothesis is that the more heavily thinned areas will experience less drought stress because the remaining trees face less competition for water. This practical trial will provide clear evidence on how thinning can be used as a tool to improve the resilience of existing forests, with monitoring focused on tree growth and soil moisture, especially during dry periods.

3. The challenge of genetic and provenance uncertainty

A key question in forestry is whether local tree populations have the genetic diversity to cope with a rapidly changing climate. Relying solely on local stock may not be the most resilient long-term strategy. The third demonstration area tackles this uncertainty head-on.

• Action: Within a mature beech stand, foresters are comparing natural regeneration of local beech with the underplanting of two different provenances of oak: one of native origin and one from a more southerly, warmer climate.
• Outcome: This creates a long-term experiment to see if trees adapted to warmer climates will outperform local ones in the future. It also widens the genetic base of the stand, providing an insurance policy against future uncertainties and enhancing the forest’s long-term adaptive capacity.

Lessons Learned

• Practical barriers exist: Implementing adaptation measures is not without challenges. The project identified several barriers, including the high cost of fencing to protect young trees, difficulties in sourcing specific planting material, and the practical complexities of future forest operations.
• Monitoring is crucial: Detailed baseline assessments were conducted before any work began, and ongoing monitoring of factors like tree mortality, soil moisture, and growth rates is essential to understand which measures are truly effective.
• Engagement and education are key: The creation of a self-guided climate change adaptation trail that includes the demonstration areas helps engage the 650,000 annual visitors and other forestry professionals, turning the forest into an outdoor classroom.

Suggested Citation

Forestry Commission (n.d.) Demonstrating climate change adaptation in Alice Holt Forest. Farnham: Forestry Commission. https://cdn.forestresearch.gov.uk/2022/05/UKFSPG026_CS5_AH-Demo.pdf

More information on: https://www.forestryengland.uk/alice-holt-forest