While these initial studies have contributed significantly towards understanding the physiology of whole ecosystems, they only represent an initial step towards the future evolution and productivity of FLUXNET. For example, the majority of the early work was produced with a subset of field sites, which was heavily biased towards coniferous and deciduous forests. With the continued growth and extended duration of the network, many new opportunities, relating to the spatial/temporal aspects of carbon dioxide exchange, remain to be explored. First, FLUXNET has expanded to include broader representation of vegetation types and climates. The network now includes numerous tower sites over tropical and alpine forests, savanna, chaparral, tundra, grasslands, wetlands and an assortment of agricultural crops. Second, the scope of many studies over deciduous and conifer forests has expanded. Several contributing research groups are conducting chronosequence studies associated with disturbance by fire and logging. From this work, scientists are learning that information on disturbance needs to be incorporated into model schemes that rely on climate drivers and plant functional type to upscale of tower fluxes to landscapes and regions—adding another level of complexity. Third, FLUXNET is partnering with other groups that are measuring the changes in phenology with networks of digital cameras, soil moisture and methane fluxes.