Presentations by Graham and Cockell showed how the biological development on Mars would be in many ways analogous to mountain and polar biological succession on Earth. One can imagine how Mars would develop biologically by imagining a descent down a tropical mountain. In terms of biology, the key question is the availability of nitrogen. In the paper by McKay, it was suggested that to recreate a biosphere on Mars there must be nitrogen present in the soil as nitrate or genetic engineering of microorganisms allowing them to take in gaseous nitrogen at present martian levels. In papers by Navarro and Heath the importance of trees as biological engines of change was emphasized.
Trees create much more biomass and produce much more oxygen than microbial ecosystems.
Navarro suggested that understanding when the first tree can grow on Mars is analogous to understanding what sets treeline on tropical mountains. The highest treeline in the world occurs on Pico de Orizaba in Mexico and this is under current intensive study. New work on the survival and functioning of insects under low pressures was presented by Cockell. He concluded that plants and insects could be introduced on Mars together. Mars is too small to have plate tectonics but Boston suggested that biological cycling should be developed to recycle nutrients.