So many people died of disease, war, and enslavement during the European conquest of the Americas that the Amazon rainforest grew back, making reduced atmospheric carbon dioxide and may have contributed to the "Little Ice Age" in the 17th century. Forests today offer a more positive hope for limiting global warming. However, the current approach is failing. An idea bio-based carbon credits is that an emitter of carbon dioxide – say an airline – can finance a project that protects trees, plants new ones or preserves other carbon containing ecosystems, such as bogs - wetlands with partially decomposed vegetation. – or mangroves. These projects are accredited according to approved methodologies by important registers such as Verra and Gold Standard. (Robin Mills)