Government spending on conservation efforts, such as management of national parks, has been patchy across the world, in part due to a lack of solid evidence of success.
Now, in a study published in Nature, researchers have shown that conservation spending of 14.4 billion international dollars over a ten-year period (during 1992-2003) resulted in a decrease in the rate of subsequent declines in biodiversity (during 1996-2008).
The analysis also provides a tool for adjusting the conservation budgets of individual countries, depending on their needs.
The researchers looked at 109 countries that are signatories to the Convention on Biological Diversity and Sustainable Development Goals, and found an average reduction of biodiversity loss of 29% per country over the twelve-year period from 1996-2008.
The study, by an international team of researchers including Dr Joseph Tobias from Imperial College London, provides the first hard evidence that conservation spending is having a substantial positive effect across a wide range of national and regional contexts.
Dr Anthony Waldron, lead author on the project, currently based at the National University of Singapore, said: "For decades, environmentalists have argued that we need to spend more on nature conservation, or face a modern mass extinction of similar magnitude to the loss of the dinosaurs.
"Yet governments and donors have been unwilling to come up with the budgets needed, often because there was little evidence that the money spent does any good. Our study shows global conservation spending in the past has had a major positive impact in reducing biodiversity loss today."
The analysis is based on a huge dataset of global conservation funding and biodiversity declines. By crunching the numbers on financial flows and conservation outcomes worldwide, the team found that biodiversity loss within each country depends largely on two factors: human economic growth and conservation spending.
While increased funding for conservation reduces biodiversity loss, the opposite is true of human economic growth - including factors such as economic development, agricultural expansion and population growth, all of which tend to negatively influence biodiversity.
By analysing the trade-offs between conservation and economic development, the researchers were able to create an algorithm that divides up responsibility for global species declines among individual countries.
This algorithm can be used to estimate how financial budgets for conservation need to be adjusted to counterbalance current or future rates of human economic growth. This could allow for smarter allocation of financial resources to conservation, helping countries achieve a better balance between economic development and the need to save species and ecosystems.
Dr Tobias said: "The findings are a rallying cry to environmentalists and policymakers. The main message is that conservation is working, but that we need to boost investment to meet international policy targets.
"In addition, the results show how conservation funding may need to change over time, and be tailored more specifically to the context of each country."