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

Drought-tolerant crops have been developed for many years, but progress has been slow because breeders have focused too intently on yield.

Questions remain as to whether other countries' success with biofuels can be replicated in Africa, says Barry Muckle.

Nuclear development is unnecessary since solar power, transmitted from North Africa and the Middle East, can supply Europe, argues Gerry Wolff.

Science, and solar energy in particular, can play a key role in providing Kenya with a better future, says Sam Aola Ooko.

Biofuels and carbon capture, two of the most favoured methods for sustainability, are a 'catastrophe for humankind', argues David Hill.

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

Biofuels have tremendous potential, but there is a danger of policy leaping ahead of the science, says Jeff McNeely.

Higher food prices due to biofuels will benefit the rural poor — it's the urban poor who will lose out, argues J. H. Tim Williams.

The biofuel industry needs to highlight the effects of biofuel production on water availability, says Mike Baker.

Biofuels production will not have a negative effect on food security in the United States, says Jacob Dubail.

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

Despite the threat of global warming, politicians will still not divert money away from global defence spending says David Hill.

Africa's science ministers have not endorsed a single model of centres of excellence, says John Mugabe, who suggests Africa must approach the issue pragmatically.

Gerry Wolff says evidence shows that the Middle East and North Africa's potential for generating solar power makes nuclear energy unnecessary.

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

Peter Orawo says that Africa must focus on developing through industrialisation rather than working to reduce the effect of climate change.

Aubrey Meyer says that while there is value in discussing the contribution of wood-burning stoves to climate change, the focus should not be taken off emissions in the North.