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Prioritisation of calamity areas for reforestation

Good practices

Nov 06, 2025
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Source: Sebastian Demmel, Stadtwald Arnsberg

To manage extensive calamity damage, forest managers and owners responsible for larger forest areas often have to prioritise reforestation efforts to keep the reforestation efforts managable. One approach to prioritising reforestation areas is the development of a color-coded categorisation system for calamity areas, according to which sites are assigned high to low priority for reforestation.

Context:

Since 2018, the combined impacts of storms, droughts and a massive bark beetle outbreak affecting Norway spruce monocultures have led to a calamity area amounting to 133.000 ha throughout the state of North-Rhine Westphalia that is in need of reforestation. 

Problem Description:

Due to resource limitations and the sheer size of the area it is not possible to reforest all of the affected calamity sites at once. Therefore, it is important to prioritise calamity areas for reforestation efforts, in particular for forest managers and owners who oversee, or own, large forest areas with multiple calamity sites. One possible approach to achieve this prioritisation is to categorise calamity areas, assigning each category a different priority for reforestation. The categorisation can be tailored to best suit the specific operational needs.

Implementation Steps:

1. Mapping of calamity areas and their site conditions.

2. Determination of a categorisation system of the calamity areas. Possible categorisation could be:
- Green: reforested or reforestation completed
- Brown: natural regeneration is present on-site (low priority)
- Yellow: under observation, natural regeneration is expected to establish itself on-site (medium priority)
- Red: high priority, lack of available seed sources of desired species and/or rapid development of competing site vegetation

Factors that should be considered in the categorisation: area size, presence of seed sources, presence of natural regeneration, site conditions/ growth potential of the sites (e.g., water and nutrient balance, site vegetation present on-site)

3. Creation of a GIS layer with the mapped information. Polygons of the calamity sites should be color coded according to the pre-determined categories.

4. Regular monitoring of calamity areas: All calamity sites of the categories brown, yellow and red should be monitored yearly to control and adjust the prioritisation as needed because site conditions can change and sites can develop differently than expected.

Stakeholder Engagement:

N/A

Knowledge Types:

The practice is based on practical local knowledge of forest managers.

Replicability:

NO, the practice has been tested only in the same context and scale; it needs to be proven for replicability and adaptability to various contexts.

Key Success Factors:

Tailored prioritisation of calamity sites
By considering factors like area size, available seed sources and local site conditions, forest managers can ensure that high-priority sites receive immediate attention while lower-priority sites are monitored and addressed as needed. Customising the approach to suit the unique challenges of each site maximises the efficiency of resource use and enhances the likelihood of successful reforestation.

Regular monitoring of sites
Regular monitoring of sites enables tracking the development of calamity sites and adjusting priorities as needed, ensuring that the reforestation efforts remain flexible and responsive to changing conditions.

Common Constraints:

Resource limitations
Even with a clear prioritisation system, forest managers may struggle to allocate adequate resources to higher-priority sites, particularly if budgets are tight or workforce availability is limited.

Technical challenges
In remote forest areas, weak GPS signals can make accurate mapping of calamity sites difficult. Additionally, some forest managers or owners may not have access to the necessary GIS software or the technical expertise to use it effectively. The cost of acquiring GIS tools and training staff can be hindering, especially for smaller operations with limited resources. Alternatively, calamity sites could be prioritised using an excel table rather than visualising it in a GIS software.

Positive Impacts:

  • Improved tree species regeneration
  • Increased climate change mitigation

Efficient Use of Resources: By prioritising reforestation efforts forest managers can allocate limited resources (time, labor, funding) more effectively. This ensures that the areas most in need of intervention receive attention first, optimising the impact of available resources and increasing the chances of successful reforestation.

Accelerated recovery of calamity sites: The systematic prioritisation of calamity areas allows for more targeted and timely interventions, speeding up the recovery process for damaged forests. High-priority areas can be addressed quickly, helping to restore forest ecosystems and their critical functions (e.g., carbon sequestration, biodiversity, water regulation) while preventing a further deterioration of high-priority sites.

Source/Author(s)
  • Larissa Janzen
Topic
  • Active Restoration
  • Planning & Upscaling
Stakeholders
  • Landowners & Practitioners
  • Planners & Implementers
Purpose
  • Climate change mitigation
  • Restoration after natural disturbances
Biogeographic region
  • Atlantic
  • Continental
Countries
  • Germany
Degradation Driver
  • Environmental
Scale Area
  • Unknown, at least 2,300 ha