In particular, natural capital is poorly represented in GDP; resources are not adequately considered as economic assets. Relative to their costs, companies and policy makers also do not give sufficient weight to the future benefits generated by restorative or protective environmental projects. As well, the important positive externalities that arise from forests, wetlands and agriculture are unaccounted for or otherwise hidden because of practical difficulties around measuring and pricing these assets. Similarly, the impact that the depletion of natural resources or increases in pollution can and do have on the future productive capacity of a nation are unaccounted for in traditional GDP estimates.