The International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) was founded in 1985 under the umbrella of United Nations Convention on long-range transboundary air pollution (CLRTAP), under the assumption that widespread forest dieback was caused primarily by atmospheric pollution. With the gradual development of knowledge on functioning of forest ecosystems it has become clear that a multitude of ecological factors play a role in the dieback of forests. Therefore the main task of the programme has become to collect and interpret the data on vitality of forests ecosystems and their reaction to various stress factors on regional, national and international level. With the reduction of sulphur emissions, the attention of the scientific community operating as a part of ICP Forests network has shifted towards the effects of nitrogen deposition, climate change and the damaging influence of ground-level ozone on forests.
Croatia takes part in the ICP Forests programme since 1987, when first large-scale and permanent monitoring of forest ecosystems started on 16×16 km grid network of plots (European network – Level 1) and intensive monitoring plots (7 plots in characteristic forest associations of Croatia – Level 2). The monitoring data are fulfilling the need of Republic of Croatia for domestic and international reporting. Nowadays monitoring is backed by forest law and regulations, and financed by the Ministry of Agriculture. Croatian Forest Research Institute is the National Focal Center of ICP-Forests. Detailed information along with annual reports on the condition of forests in Croatia can be found at www.icp.sumins.hr.