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protected areas (pAs) are a foundational and essential strategy for reducing biodiversity loss. However, many pAs around the world exist on paper only; thus, while logging and habitat conversion may be banned in these areas, illegal activities often continue to cause alarming habitat destruction. in such cases, the presence of armed conflict may ultimately prevent incursions to a greater extent than the absence of conflict. Although there are several reports of habitat destruction following cessation of conflict, there has never been a systematic and quantitative "before-and-after-conflict" analysis of a large sample of pAs and surrounding areas. Here we report the results of such a study in colombia, using an open-access global forest change dataset. By analysing 39 PAs over three years before and after colombia's peace agreement with the Revolutionary Armed forces of colombia (fARc), we found a dramatic and highly significant increase in the deforestation rate for the majority of these areas and their buffer zones. We discuss the reasons behind such findings from the Colombian case, and debate some general conservation lessons applicable to other countries undergoing post-conflict transitions. The growing warfare ecology literature reports both negative and positive effects of conflict for biodiversity and the natural environment 1-3. This also applies to deforestation, which can be either increased or decreased depending on the specific complex socio-ecological dynamics linked to the conflict itself 3-5. Increased deforestation during conflict is reported for several regions of the world 6 , including Democratic Republic of Congo (DRC) and Liberia 7 or Myanmar and Cambodia 8. In some cases, conflict reduces the institutional capacity to enforce laws and effectively manage the use or protection of natural resources, e.g. as reported for Kenya 9 , DRC 10 , Nepal 11 , and Colombia 5. In other cases, the displacement of people escaping or forced to leave conflict areas, the basic mechanism for the 'refuge effect' 12 , can prove beneficial for habitat and biodiversity protection, e.g. by limiting the pressure of resource extraction 13-15. The demilitarized Zone between North and South Korea is a good example of such a refuge 16. Conflict can largely disrupt economic activities 1 , such as timber logging in Nicaragua 17 , or farming, as in Sierra Leone 18. In the Chechen wars and in the nearby Nagorno-Karabakh conflict, agricultural land was abandoned in warzones, along with reported low re-cultivation rates after the cessation of the conflict 19,20. In other cases post-conflict development results in higher threats to forested ecosystems than conflict

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The rapidly expanding network of roads into the Amazon is permanently altering the world’s largest tropical forest. Most proposed road projects lack rigorous impact assessments or even basic economic justification. This study analyzes the expected environmental, social and economic impacts of 75 road projects, totaling 12 thousand kilometers of planned roads, in the region. We find that all projects, although in different magnitudes, will negatively impact the environment. Forty-five percent will also generate economic losses, even without accounting for social and environmental externalities. Canceling economically unjustified projects would avoid 1.1 million hectares of deforestation and US$ 7.6 billion in wasted funding for development projects. For projects that exceed a basic economic viability threshold, we identify the ones that are comparatively better not only in terms of economic return but also have lower social and environmental impacts. We find that a smaller set of carefully chosen projects could deliver 77% of the economic benefit at 10% of the environmental and social damage, showing that it is possible to have efficient tradeoff decisions informed by legitimately determined national priorities.

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