At the Cuyabeno Wildlife Reserve in northern Ecuador, biologists and park rangers are using butterflies, the "very small, delicate insects with very colourful wings", to "understand what could happen with climate change". The decade-long study, supported by the US-based Rainforest Partnership, focuses on the Amazon rainforest, where biologist Maria Fernanda Checa says there has been a "worrying" 40% decline in butterfly numbers. IMAGES AND SOUNDBITES