Maps of the potential spatial distribution of the main species

Maps of the potential spatial distribution of the main species in Romania

The IPCC has developed a set of short- and medium-term projections for the concentration of the main greenhouse gases (radiative forcing gases). Emissions trajectories depend mainly on political and economic choices and are therefore referred to as Representative Concentration Pathways (RCPs). Each scenario shows a concentration increase curve that results in a different level of radiative forcing: 2.6, 4.5 or 8.5 W.m-2. Given recent social and climate trends, the scenario based on a radiative forcing of 2.6 W.m-2 must be abandoned because it is already outdated.

Emission scenarios are used to create global and regional climate predictions through circulation models. Regionalizing predictions is a difficult process, and predictions vary greatly from model to model. To model the distribution of trees, a set of 18 models were combined to generate optimistic, medium, or pessimistic predictions. The optimistic version is based on the model that estimates the smallest water deficit of these 18 models. The average predictions represent the average of the predictions of the 18 models and the pessimistic variant is based on the model that predicts the highest water deficit.

The tree distribution model used here is the IKS model, implemented in the ClimEssences platform (https://climessences.fr/). The model was subjected to an extensive calibration based on a very large dataset on a European scale (data from the National Forest Inventories of most EU countries, including Romania).
The IKS model is a bioclimatic compatibility model, with the aim of predicting the presence or absence of a certain species of forest trees depending on limiting climatic parameters. The presence-absence estimates are based on three indicators: the annual water deficit, the annual minimum temperature and the annual sum of degree-days (the sum of the temperatures of the days above 5ºC).
The IKS model is used here to model the distribution of species under current conditions, then in future climatic conditions, such as the two scenarios RCP4.5 and RCP8.5. For each RCP scenario, having a variability in local climate predictions, three variants were calculated: the optimistic variant, the medium variant and the pessimistic variant.
The choice of the IKS model was based on the fact that it is the model that has the best performance in determining the presence-absence of forest tree species in the current climatic conditions.

The maps show 4 zones: the compatibility zone where the species can grow in all 3 variants, compatibility zones for the medium and optimistic variants, compatibility zones only for the optimistic variant, and the zone where the species is not compatible with any variant.

RCP4.5 scenario
The distributions are based on future climate data, using the average of the predictions of 18 climate models. The RCP4.5 scenario is considered an average scenario, but predictions for average annual temperatures still show an increase of 2.15ºC by 2070 compared to current temperatures.

Scenariu RCP8.5

Scenariul RCP8.5 este considerat mai dur, iar predicțiile pentru temperaturile medii anuale arată o creștere cu 3,6ºC la orizontul anului 2070.