A new letter in the Proceedings of the National Academy of Sciences (PNAS) highlights an exciting new ability in global remote sensing: by using fluorescence data from satellites already in orbit, some scientists now believe they can provide a more accurate look at the level of photosynthetic activity in large vegetated areas. Even better, there’s already a super-powered successor satellite in the works, meaning that this new technique could shortly give scientists a much better understanding of how global food crops are responding to climate change.

The principle at work is actually very old, which connects specific wavelengths of fluorescent light from vegetation to the overall level of photosynthetic activity in that vegetation — but for years, this principle was applied at the “leaf level,” and was not particularly helpful for global-scale science. But some researchers thought that despite the faintness of the signal, dense green areas ought to give off enough fluorescence to be usefully measured from space. In 2011 and 2014, they were able to incorporate the data from Japan’s Greenhouse Gases Observing Satellite (GGOS) and Europe’s Global Ozone Monitoring Experiment 2 (GOME-2), both of which were already in orbit.

This week’s letter calls the technique “probably the most thrilling development in remote sensing and global ecology of recent years.” That’s because when the 2014 study incorporated the new fluorescence data, they found that the new best estimates for photosynthesis were actually quite a bit higher than previous numbers. In parlance, the area’s Gross Primary Productivity (GPP) was 50-75% higher than predicted — photosynthesis was progressing faster, more carbon was being cycled through the system. The results have motivated significant interest within the field.

What really has scientists excited, however, is the European Space Agency’s planned FLuorescence EXplorer (FLEX) satellite, which will allow an enormous increase in their observational capabilities for fluorescence. This should allow an all-new level of detail in studying the real state of global vegetation — not the percent covered with leaves, but the actual systemic throughput of the ecosystem. Prior estimates were based on things like the percentage of radiation absorbed and the chlorophyll content on the ground — but neither of these readings could directly measure the actual level of activity in those systems.

GPP can be measured over time, and can even watch the output effects of plants’ day-night cycles. The net effect of all these improvements is a substantial boost in accuracy and system quality. As the image to the right shows, the readers can be used to interpret where vegetation is stressed versus where it’s growing well. This data could also allow detection of early warning signs of ecosystem-level stress, granting the ability to predict certain oncoming downturns in crop yield, and potentially head them off. It might even be possible to indirectly detect pollution or illegal dumping of certain chemicals — an area of stressed vegetation that ought to show as healthy could trigger a follow-up ground-based investigation.

All of this will be important information to gather, as numerous nations brace for the continuing effects of climate change. Between increasing levels of drought and increasing need for high-output irrigated crops, the distribution of arable farmland will be of great importance. If one area of the world is becoming more or less photosynthetically active, it could prompt large-scale changes in global investment and the economic futures of a huge number of people.

Estimates of global-scale GPP values were low, having simply plugged cruder space-based measurements into mathematical models for carbon cycling. These sorts of more direct measures of the actual productive health of the Earth’s biosphere could be important in helping scientists plot the Earth’s trajectory in the coming years, to predict its most likely position in the coming decades.