We know that lichen cover in polar and high altitude regions may change due to grazing or climate change. Some previous studies have found that removal of lichen reduces the albedo and potentially changes the temperature, while others have focused on lichen's evapotranspiration. The purpose of this thesis is to quantify the importance of lichens for the entire surface energy balance as a whole, and the potential effects this may have on the temperature. This is investigated by implementing lichen as a new plant functional type (PFT) in the community land model (CLM4.5), and comparing the surface energy balance for lichen with other PFTs that may replace lichen. Comparisons are made between both idealised single column cases and for a larger grid in Finnmark with estimated lichen heath amounts from distribution modelling. Validation of the choice of parameter values for the lichen implementation is initiated by measuring the maximum amount of water in lichen and the rate of drying, but more validation is needed. The results show that the properties that separate lichen from other vegetation, especially the albedo and evapotranspiration, give rise to surface energy fluxes that differ from other PFTs. The changes in the surface energy fluxes also influence the temperature. Lichen cover has a higher albedo than most other PFTs, which works to decrease the skin temperature. At the same time, the latent heat flux for lichen is very variable due high water holding capacity and lack of a root system. On average the latent heat flux is small for lichen, which works to increase the temperature. Because the simulations are performed offline, the surface energy fluxes' full potential for influencing the air temperature is not reached. However, the results suggest that lichen potentially can be important for the surface energy balance and local climate when studying the effects of vegetation changes in polar regions.