Conservation aid has been effective in preventing deforestation in many areas. For example, a 2018 study found that conservation aid reduced deforestation in the Amazon rainforest by 17% between 2000 and 2012. Another study found that conservation aid helped to reduce deforestation in Indonesia by 50% between 1990 and 2015.

However, conservation aid is not always effective in preventing deforestation. For example, a 2019 study found that conservation aid had no significant impact on deforestation in the Congo Basin between 2000 and 2014. Another study found that conservation aid actually increased deforestation in some areas of the world, such as in the Brazilian Cerrado.

The effectiveness of conservation aid in preventing deforestation depends on a number of factors, including the type of aid, the amount of aid, the location of the aid, and the political and economic context in which the aid is provided.

Some types of conservation aid are more effective than others in preventing deforestation. For example, aid that is used to support indigenous peoples' rights and livelihoods has been shown to be more effective in preventing deforestation than aid that is used to support conservation efforts that do not involve indigenous peoples.

The amount of conservation aid also matters. A 2019 study found that the effectiveness of conservation aid in preventing deforestation increased as the amount of aid increased. However, the study also found that the effectiveness of conservation aid decreased as the amount of aid increased beyond a certain point.

The location of conservation aid also matters. A 2017 study found that conservation aid was more effective in preventing deforestation in areas that were already experiencing high levels of deforestation than in areas that were not experiencing high levels of deforestation.

The political and economic context in which conservation aid is provided also matters. A 2018 study found that conservation aid was more effective in preventing deforestation in countries that had strong environmental laws and regulations than in countries that did not have strong environmental laws and regulations. Another study found that conservation aid was more effective in preventing deforestation in countries that had low levels of corruption than in countries that had high levels of corruption.

Overall, conservation aid can be an effective tool for preventing deforestation, but its effectiveness depends on a number of factors.