The graph below (taken from a paper Environment assisted quantum transport by Patrick Rebentrost, Masoud Mohseni, Ivan Kassal, Seth Lloyd and Alán Aspuru-Guzik) shows the calculated efficiency of transport (blue curve) of an exciton through at network in the presence of a dissipative and dephasing environment. The horizontal scale is the magnitude of the dephasing rate. n.b. it is a logarithmic scale and spans 10 orders of magnitude. The vertical line is the estimated dephasing rate at room temperature.
To me the curve shows that the efficiency is quite insensitive to the environment, i.e. it is greater than 80 per cent for dephasing rates varying by eight orders of magnitude! In terms of biological functionality I would say that the environment matters little to the efficiency, except when the system couples very strongly to the environment.
However, other people interpret this graph in a very different way. In a 2010 paper in PNAS, Long-lived quantum coherence in photosynthetic complexes at physiological temperature, the authors (led by Greg Engel from University of Chicago) state
theoretical studies incorporating both incoherent and coherent transfer as well as thermal dephasing predict that environmentally assisted quantum transfer efficiency peaks near physiological temperature
we ... observe quantum coherence lasting beyond 300 fs, showing that evolution has had the opportunity to exploit the theorized environmentally assisted quantum transport (EnAQT) mechanism for biological function.What do you think?