It is often assumed that trees grown to offset CO{sub 2} emissions need then to be preserved in order to keep the CO{sub 2} from returning to the atmosphere. My contention is that, in terms of atmospheric CO{sub 2}, a tree performs equivalently if it stores carbon or if its conversion to CO{sub 2} displaces some other source of CO{sub 2} that would otherwise be released. There is no difference in atmospheric CO{sub 2} if we burn coal and save trees or if we burn trees and save coal. This manuscript compares the alternatives. Through a simple model of carbon flows I compare net reductions of emissions of CO{sub 2} to the atmosphere for various combinations of: (1) the existing land use, (2) the anticipated growth rate of trees, (3) the fate of trees once they reach maturity, (4) the efficiency with which trees are used once harvested, and (5) time. The analysis focuses on the net carbon benefit and does not consider other factors that would enter into forest management decisions. The model shows that when there is an existing forest and either low growth-rate potential or a large energy cost involved with harvest and use, the most carbon …

In this paper we outline a model which incorporates development processes into an evolutionary frame work. The model consists of three sectors describing development, genetics, and the selective environment. The formulation of models governing each sector uses dynamical grammars to describe processes in which state variables evolve in a quantitative fashion, and the number and type of participating biological entities can change. This program has previously been elaborated for development. Its extension to the other sectors of the model is discussed here and forms the basis for further approximations. A specific implementation of these ideas is described for an idealized model of the evolution of a multicellular organism. While this model doe not describe an actual biological system, it illustrates the interplay of development and evolution. Preliminary results of numerical simulations of this idealized model are presented.