Over the last decade, genetically modified crops have become widespread in agriculture. One of the more successful of these are Bt crops - transgenic plants that express genes derived from Bacillus thuringensis. These genes allow the plants to produce toxins which specifically affect certain groups of insects. Since these plants do not need to be sprayed, and since the toxins are relatively specific, the environmental effects appear to be lower than conventional agriculture.

In response to Wright and Muller-Landau’s paper on the future of tropical forests (which suggests that declining rural populations can allow forest recovery; see my previous post), Sloan pointed out reduced rural population often leads to increased deforestation. Really that’s not a huge surprise - peasant farmers tend to have limited labour to clean and plant land, and being capital-limited they tend not to be able to switch to mechanised agriculture.

Anyone who has conducted field research knows that the very process of collecting data alters the system that you are studying. As you walk across a field, forest or stream to collect data, your footfalls trample vegetation, they compact the soil, they scrape algae off the rocks. Survey work usually involves a single visit to a site - as long as you avoid sampling from the areas you have trampled, it’s usually pretty safe to assume that your presence is unlikely to have affected the data that you have collected. Permanent plots are a different matter - because these plots are repeatedly sampled, there is cumulative damage. In larger plots, permanent trails may be established within plots.

Since we can’t avoid these effects, the real question is whether the effects are significant. Ecological systems are inherently heterogeneous. Does the effect of disturbance fall within the range of natural variability within the sample? That’s what really matters when it comes to data collection. In a forthcoming paper in the journal Biotropica, Liza Comita and Gregory Goldsmith “sought to quantify the significance and spatial extent of research trail impacts on the structure and dynamics of the seedling layer in the 50-ha permanent forest dynamics plot on Barro Colorado Island (BCI), Panama”.

Anoop Sindhu and colleagues report on a gene that may have played a key role in the evolution of grasses. The gene, Hm1, provides resistance against Cochliobolus carbonum race 1 (CCR1), a fungus that is capable of attacking and killing corn at any stage of its development (images of CCR1 infection). While CCR1 is only known to affect corn, the gene Hm1 and its relatives are present throughout the grass family, but are absent from other lineages.