We need a clearer understanding of disease patterns and ecosystem impacts before embarking on eradication strategies, says Ummer Rashid Zargar.

GM crops have large benefits and pose no unique safety concerns, writes head of the Brazilian Biosafety Association, Leila Oda.

Indigenous and wild cassava species offer a cheap source of key nutrients, says Brazilian agriculturalist Nagib Nassar.

Encouraging the spread of probiotic foods that promote healthy gut bacteria could help developing countries tackle obesity, says Kingsley Anukam.

Markku Lehtonen argues that the Brazilian bioethanol sector must be looked at regionally to ensure social and green issues are dealt with.

There are good and bad biofuel programmes, and we would do well to distinguish between them, says Steven Savage.

The developing world needs 'big projects, not small ideas' — and nuclear power is a viable and necessary solution, argues Marje Hecht.

Developing countries need global reform as well as focused aid to beat poverty, argues Paul Collins of War on Want.

Warea Orapa says that tilapia fish — hailed as a method of controlling mosquitoes — can cause damage when introduced into new ecosysems.

There is little resistance to the pesticide pyrethrum at present, but use in bednets could change this, says Christiaan Kooyman.

Alexander Boksenberg argues that the unique potential of UNESCO's science strategies is substantial.

Cristobal Valencia Ramirez describes Venezuela's take on innovation and enterprise, pointing out that its policies have been in place for at least five years.

Sam Lanfranco argues that the fame of the One Laptop Per Child initiative has prevented more worthy initiatives from receiving the media attention they deserve.

Charlene Richards says a new science policy institute planned in Jamaica must focus first on developing policies for training and retaining scientific talent.

Emilio Mayorga and Anthony Aufdenkampe clarify differences between carbon stored in rainforest trees and carbon released by forest streams.

Robert Abdenur disagrees with claims that Brazil could have had suspect motives for not allowing access by inspectors to its uranium enrichment facilities.

Marcelo Leite says it is regrettable that avoidance of deforestation is not included in the Kyoto Protocol's clean development mechanism because a large proportion of Brazil's emissions come from land use in the Amazon region.

R. Aldrovandi and J. G. Pereira express their concerns about the increasing difficulties faced by Colombian researchers travelling to certain countries.