Much of the destruction of rainforests occurs because no one knows it is happening until too late. Satellites could change that, so forest protectors are subscribing to regularly updated photographs in an effort to interrupt rounds of destruction. When researchers decided to test if this eyes-in-the-sky approach actually works they found something surprising – the new technology has already saved a lot of Africa forest, but appears to have no measurable benefit in South America or south-east Asia.
Rainforests are being devoured worldwide, accounting for a major portion of greenhouse gasses, and an even bigger share of the current catastrophic rate of extinction. Some of this destruction is government-approved, but a lot is occurring illegally in officially protected places. With policing resources limited, those attempting to save these areas often only find out about the damage well after it is done.
Global Forest Watch (GFW) offers satellite updates of canopy loss at a spatial resolution of around 30 meters (100 feet) whenever a Landsat 7 or 8 satellite (joint NASA-USGS Earth observatory satellites) gets an uninterrupted view of an area. For the tropics, that is every eight days when clouds don't block the view.
Government agencies and conservation organizations that sign up to GFW receive an alert when an algorithm detects a change in forest cover for their area of interest, allowing them to interrupt loggers in the act. It's great in theory, but Dr Fanny Moffette of the University of Wisconsin, Madison, knew better than to take the effectiveness of programs like this for granted.
In Nature Climate Change, Moffette and co-authors report access to GDW alerts was associated with an 18 percent reduction in deforestation rates in Africa compared to 2011-2016 baseline. Cameroon, where the alerts have been used most heavily, has made major inroads into the problem of illegal deforestation. Meanwhile, damage continued unabated in areas where alerts were not used.
If all this seems a little obscure, consider the significance of an 18 percent reduction in loss of forests on just one continent. Moffette and co-authors estimate the area these alerts have saved amounts to almost 500 square kilometers (193 square miles) a year. Multiplying by typical carbon storage for forests in the area that means some 14 million tonnes of carbon a year that would be released is saved. The majority of African nations, including some quite large ones, release less than that by burning fossil fuels each year.
In purely monetary terms these near-weekly tweets/emails are saving hundreds of millions of dollars worth of carbon emissions, far more, the authors note than the cost of the system. No one knows how to calculate the value of the species saved from extinction, nor other long-term benefits of the preserved forests, but it would certainly be immense.
The authors think political unrest in Venezuela and Columbia may have undermined the effectiveness of the alerts in South America. In many Asian nations up-to-date information was already available, before the alerts started, suggesting obstacles to forest protection lie elsewhere.