European forest monitoring: improvements needed

With 227.4 million hectares (34.8 % of the land area; Source: State of Europe's Forests), forests represent an immense resource in Europe. The intention to promote their consistent monitoring is, therefore very welcome.

The European Commission's stated intention to "minimise the extent to which Member States need to adapt their data collection methods" seems elusive when the proposal de facto ignores the extensive structures and resources already in place in each country. These structures include national coordination centres, networks of monitoring plots (see fig. 1), expertise in different monitoring areas, manuals with harmonised methods covering all forest ecosystem compartments, data control routines and standardised data reporting formats and procedures.

The European Commission's proposal emphasises carbon sequestration in forests and is largely concerned with trees and wood resources. Little is planned, for example, in relation to the health and vitality of forests, a key aspect when considering the resilience of forests.

The health of forests depends on many different factors. Nevertheless, the proposal only mentions ‘defoliation’. The proposal envisages using the remotely sensed Leaf Area Index (LAI) for this purpose. However, this parameter cannot serve as an adequate measure of needle and leaf loss if it is not validated and calibrated on the ground. In the national forest inventories (NFI), the only ground-based monitoring systems explicitly mentioned in the proposal, data on defoliation is not routinely collected. Thus, there is a risk that forest health will be only inadequately described.

In contrast, needle/leaf loss is the key characteristic for ICP Forests and has been analysed on an annual basis for decades in both Level I and Level II networks (see fig. 3 - details in the original article). The approximately 7000 ICP Forests plots with 30-year time series are an important existing basis for the assessment of forest health in space and time. In this context, the remote sensing data proposed by the European Commission could be used for spatio-temporal modelling purposes based on ground-based observations rather than as unvalidated, stand-alone measurements.

Biodiversity is another focus of the proposal. Specific data on tree species composition and abundance, deadwood and forest birds are requested. The presence of invasive plant and tree species, the diversity of non-tree vegetation and endangered species are also mentioned, but with few methodological details and subject to the future development of monitoring. 

However, there are already recognised, internationally agreed methods for monitoring the diversity of plants and animals (e.g. ground vegetation, epiphytic lichens). Others have been widely and successfully tested at European level (e.g. mycorrhiza) or are currently being developed and trialled using the ICP Forests Plot infrastructure (e.g. metabarcoding for biodiversity in soil and water samples and in insect traps).

Data comparability, quality and availability are regarded as strategic objectives in the European Commission's proposal. But how is this to be achieved? It is particularly problematic that the responsibility for data quality is left to the Member States. This could lead to major national differences. There are already many multidisciplinary harmonisation activities that have been carried out internationally within the framework of the NFI and ICP Forests and that can be easily used.

The European Commission's proposal emphasises that it is based on the latest scientific findings. However, it remains unclear what is meant by this. For example, the combination of remote sensing and terrestrial data has been practised since decades. Why does the European Commission not draw on the wealth of international monitoring networks and research infrastructures that have been developed during this time? Some examples for such existing networks are:
ICP Forests, ICP Integrated Monitoring, eLTER, ICOS

With their vast data archives, these networks would make an invaluable contribution, particularly regarding the 'process understanding' part of monitoring, an essential missing component in the European Commission's proposal. This omission is not only surprising because it detracts from the proposal's ability to achieve its stated objectives. It is also surprising given that the EU (i) has played a key role in establishing and funding these existing systems, (ii) is a signatory to the UNECE Air Convention, and (iii) is investing in projects designed to promote future monitoring and where various communities (including NFIs, ICP Forests and remote sensing) are already collaborating. Examples for such projects are:
HORIZON EUROPE PathFinder, FORWARDS, MoniFun, COST Action CLEANFOREST

In order to achieve the goal of comprehensive and coherent forest monitoring, existing resources and monitoring networks should be utilised and strengthened through integrative approaches (such as the SwissAIM initiative). This includes the promotion of co-operation between Member States and the use of international networks. Such an approach could improve the effectiveness of monitoring while minimising the burden on national systems. Specifically:

• The monitoring concept should be revised and further developed by utilising existing internationally coordinated networks in order to reduce the burden on Member States and achieve the European Commission's objectives.
• Synergies between existing monitoring networks should be identified and utilised (with any gaps to be filled) to enable Europe-wide monitoring.
• An institutional framework for a co-operative, integrated forest monitoring system should be developed to facilitate co-operation between existing networks and to strengthen the role of the EU and international institutions.

Climate change will significantly alter forests and pose major challenges for forest management. A European Commission proposal for a new forest monitoring programme aims to improve data quality and availability. In order to accurately assess the state of forests and predict future developments, more precise data is needed than national programmes can provide, and data from ground-based monitoring programmes must be combined with remote observation data. Experts recommend involving existing international monitoring networks more closely and creating an institutional framework for cooperation. This would increase the effectiveness of monitoring and reduce the burden on national systems. Conceptual adjustments are necessary to achieve the objectives of the proposal and to ensure the sustainable management and protection of European forests.