What was done
S. Joseph Wright of the Smithsonian Tropical Research Institute in Panama reviews what is known about "ongoing anthropogenic change in tropical forests with an eye toward understanding how these forests might respond to increasing anthropogenic pressure," noting that "understanding and mitigating the impact of an ever-increasing population and global economic activity on tropical forests is one of the great challenges currently facing biologists, conservationists and policy makers."

What was learned
After discussing local anthropogenic phenomena, such as deforestation, secondary forest succession, land-use change, invasive species and poaching, Wright comes at last to a consideration of global anthropogenic effects.  Here, he finds that "the evidence for global effects suggests that a massive reorganization of the structure and dynamics of tropical forests is already underway."  This evidence, in his words, "comes almost exclusively from repeated censuses of tree plots," an approach that he notes has at times been controversial, especially since the historical rise in the air's CO2 content has been implicated as possibly playing a major role in the observed changes.  In this regard, Wright further notes that "the tropics lack a single forest-level elevated CO2 experiment and have very few, if any, long-term experiments in secondary forest," thus suggesting that long-term CO2 enrichment experiments be initiated in these areas, a proposal we also find attractive.

What it means
In what sounds a lot like a challenge to those who find no redeeming qualities in the ongoing rise in the air's CO2 content, Wright concludes that "until new data become available, we must accept the available evidence indicating that global change is causing a massive restructuring of lowland tropical forests with rapid increases in aboveground biomass, basal area, stem density, mortality, recruitment and the relative importance of lianas and canopy tree species," citing the findings of Phillips et al. (2002), Baker et al. (2004), Laurance et al. (2004), Lewis et al. (2004) and Phillips et al. (2004) in support of this list of real-world observations.

References
Baker, T.R., Phillips, O.L., Malhi, Y., Almeida, S., Arroyo, L., Di Fiore, A., Erwin, T., Higuchi, N., Killeen, T.J., Laurance, S.G., Laurance, W.F., Lewis, S.L., Monteagudo, A., Neill, D.A., Núñez Vargas, P., Pitman, N.C.A., Silva, J.N.M. and Vásquez Martínez, R. 2004. Increasing biomass in Amazonian forest plots.  Philosophical Transactions of the Royal Society of London Series B - Biological Sciences 359: 353-365.

Laurance, W.F., Oliveira, A.A., Laurance, S.G., Condit, R., Nascimento, H.E.M., Sanchez-Thorin, A.C., Lovejoy, T.E., Andrade, A., D'Angelo, S. and Dick, C.  2004.  Pervasive alteration of tree communities in undisturbed Amazonian forests.  Nature 428: 171-175.

Lewis, S.L., Phillips, O.L., Baker, T.R., Lloyd, J., Malhi, Y., Almeida, S., Higuchi, N., Laurance, W.F., Neill, D.A., Silva, J.N.M., Terborgh, J., Lezama, A.T., Vásquez Martinez, R., Brown, S., Chave, J., Kuebler, C., Núñez Vargas, P. and Vinceti, B.  2004.  Concerted changes in tropical forest structure and dynamics: evidence from 50 South American long-term plots.  Philosophical Transactions of the Royal Society of London Series B - Biological Sciences 359: 421-436.

Phillips, O.L., Baker, T.R., Arroyo, L., Higuchi, N., Killeen, T.J., Laurance, W.F., Lewis, S.L., Lloyd, J., Malhi, Y., Monteagudo, A., Neill, D.A., Núñez Vargas, P., Silva, J.N.M., Terborgh, J., Vásquez Martínez, R., Alexiades, M., Almeida, S., Brown, S., Chave, J., Comiskey, J.A., Czimczik, C.I., Di Fiore, A., Erwin, T., Kuebler, C., Laurance, S.G., Nascimento, H.E.M., Olivier, J., Palacios, W., Patiño, S., Pitman, N.C.A., Quesada, C.A., Saldias, M., Torres Lezama, A., B. and Vinceti, B.  2004.  Pattern and process in Amazon tree turnover: 1976-2001.  Philosophical Transactions of the Royal Society of London Series B - Biological Sciences 359: 381-407.

Phillips, O.L., Martinez, R.V., Arroyo, L., Baker, T.R., Killeen, T., Lewis, S.L., Malhi, Y., Mendoza, A.M., Neill, D., Vargas, P.N., Alexiades, M., Ceron, C., Di Fiore, A., Erwin, T., Jardim, A., Paiacios, W., Saidias, M. and Vinceti, B.  2002.  Increasing dominance of large lianas in Amazonian forests.  Nature 418: 770-774.