Although indigenous farmers and other traditional peoples have disturbed Amazonian forests for centuries, few studies investigate the effects of these disturbances on biodiversity. This short-term study investigates how bird assemblages are affected by agricultural practices adopted by the residents of a national park in the Brazilian Amazon. Twelve sites in secondary forest (four sites in three age categories) and 12 sites in primary forest were selected for bird sampling. Audio-visual censuses of birds were conducted in small plots (1 ha) of young secondary growth (4–5 y), middle-aged (7–15 y), and old (20–35 y) secondary forests. Each site in secondary forest had a corresponding control site in adjacent primary forest. Young secondary growth had fewer species than old secondary and primary forests. Bird species richness was similar in middle-aged, old secondary and primary forests. Bird communities of young secondary habitat were dominated by species normally found in open habitats, such as agricultural fields and igapó flooded forests. The bird species composition of young secondary growth was more similar to that of middle-aged forest, which in turn was more similar to that of old secondary forests. Bird species composition differed between young secondary growth and old secondary forests and primary forests and between middle-aged secondary and primary forests. Nectarivore/insectivores and frugivore/insectivores of monospecific flocks are significantly associated with secondary forests, especially in initial stages of forest regeneration. In contrast, specialized insectivorous birds that join mixed-flocks show a significant association with primary forest.

There is much discussion of the probability of transgene flow from transgenic crop varieties to landraces and wild relatives in centers of origin or diversity, and its genetic, ecological, and social consequences. Without costly research on the variables determining gene flow, research on transgene frequencies in landrace (or wild relative) populations can be valuable for understanding transgene flow and its effects. Minimal research requirements include (1) understanding how farmer practices and seed systems affect landrace populations, (2) sampling to optimize Ne/n (effective /census population size), (3) minimizing variance at all levels sampled, and (4) using Ne to calculate binomial probabilities for transgene frequencies. A key case is maize in Mexico. Two peer-reviewed papers, based on landrace samples from the Sierra Juárez region of Oaxaca, Mexico, reached seemingly conflicting conclusions: transgenes are present (Quist and Chapela, 2001, Nature414: 541–543; 2002, Nature416: 602) or “detectable transgenes” are absent (Ortiz-García et al., 2005, Proc. Natl. Acad. Sci. USA102: 12338–12343 and 18242). We analyzed these papers using information on Oaxacan maize seed systems and estimates of Ne. We conclude that if Quist and Chapela’s results showing presence are accepted, Ortiz-García et al.’s conclusions of no evidence of transgenes at detectable levels or for their introgression into maize landraces in the Sierra de Juárez of Oaxaca are not scientifically justified. This is because their samples are not representative, and their statistical analysis is inconclusive due to using n instead of Ne. Using estimates of Ne based on Ortiz-García et al.’s n, we estimate that transgenes could be present in maize landraces in the Sierra Juárez region at frequencies of ~1–4%, and are more likely to be present in the 90% of Oaxacan landrace area that is not mountainous. Thus, we have no scientific evidence of maize transgene presence or absence in recent years in Mexico, Oaxaca State, or the Sierra Juárez region.

Genetically engineered transgenic crop varieties (TGVs) have spread rapidly in the last 10 years, increasingly to traditionally-based agricultural systems (TBAS) of the Third World both as seed and food. Proponents claim they are key to reducing hunger and negative environmental impacts of agriculture. Opponents claim they will have the opposite effect. The risk management process (RMP) is the primary way in which TGVs are regulated in the US (and many other industrial countries), and proponents claim that the findings of that process in the US and its regulatory consequences should be extended to TBAS. However, TBAS differ in important ways from industrial agriculture, so TGVs could have different effects in TBAS, and farmers there may evaluate risks and benefits differently. To evaluate some potential impacts of TGVs in TBAS we used the RMP as a framework for the case of Bt maize in Mesoamerica and Cuba. We interviewed 334 farmers in Cuba, Guatemala and Mexico about farming practices, evaluations of potential harm via hypothetical scenarios, and ranking of maize types. Results suggest high potential for transgene flow via seed, grain and pollen; differences in effects of this exposure in TBAS compared with industrial agriculture; farmers see some potential consequences as harmful. Perceptions of harm differ among farmers in ways determined by their farming systems, and are different from those commonly assumed in industrial systems. An RMP including participation of farmers and characteristics of TBAS critical for their functioning is necessary to ensure that investments in agricultural technologies will improve, not compromise these agricultural systems.