**5.2 Prospects for global modelling**

Vegetation plays a significant role in global climate, water, energy and biogeochemical cycles, particularly concerning carbon, with approximately one quarter of atmospheric carbon dioxide fixed annually as gross primary production. To accurately model this and other land surface processes in General Circulation Models (GCM), properties such as radiation absorption, plant physiology, surface characteristics and climatology are required. These models require multitemporal global datasets that can only be obtained from remotely sensed sources.

Computer-generated models of the biosphere provide a valuable means to improve understanding of the immensely complex interactions between interdependent systems affecting the Earth. By their very nature, models function as generalisations of reality and a series of component models replicating the interplay of systems often provide input to complex broader-themed Biosphere models.

Dynamic Vegetation Models are particularly valuable in enabling prediction of the carbon balance under changing ecosystem structure and composition brought about by climatic changes. Vegetation is often represented within each grid cell as generalised Plant Functional Types and climate-driven habitat changes are used to model vegetation succession and plant lifecycle. Where vegetation height is currently considered as static over time, models could benefit from future global lidar observations of vegetation height (e.g. Lefsky, 2010, Los *et al.*, 2011) or biomass, particularly if signal sensitivity permits growth over the sensor lifetime to be observed. Furthermore, the use of lidar could inform validation of LAI, fractional canopy cover or NDVI products (Los *et al.,* 2008, 2011) which are produced using indirect relationships with optical reflectance properties.
