There's nothing incorrect about the study. What they did was look at satellite maps and determine how much land was covered by trees. That seems like a logical approach. They concluded-- and there's no reason to doubt them-- that more of the Earth's land surface is under tree cover than 40 years ago. That's extremely useful knowledge.
What they didn't do was look at the KINDS of plants that were growing. They accomplished their goal, but now it's up to other scientists to react to that data and use it to drive further investigations. No one is saying the study is wrong, just that it's incomplete.
This is why I get annoyed when people blame scientists or the media for things. The whole point of science is to seek answers to tough questions. When it comes to climate change or things like that, it's pushing the envelope of knowledge. So no study should be treated as conclusive. At the same time, just because you have two findings or two interpretations that disagree, doesn't mean you throw your hands up either. Each of those things is a piece of the puzzle.
The problem is that people are extremely bad at dealing with uncertainty and risk. And with more information at their hands than ever, it's simultaneously harder to think about issues if you really try (because of conflicting info.) while easier than ever to just pick a side and have tons of stuff to back you up.
The article from Nature is easy to obtain online. It goes over some of this stuff. It says that the major loss is coming from the tropics, that there is some re-forestation from abandoned farms going back to nature, that some re-forestation efforts seem to have been successful, but some of the coverage is coming from tree farms and global warming as well.
It doesn't draw the conclusions people want it to draw. There is no "yes/no" or "scale of 1-10" answer. Which is how it should be in science.
You see this attitude in how people treat news as well. People will say "Well, I read some left wing articles. And then I read some right wing articles. I take what I read and make up my own mind." They think this is a very enlightened approach and pat themselves on the back. But really, it's a fundamentally stupid approach.
The average person is not hanging out in 1600 Pennsylvania Avenue or 10 Downing Street. They're not experts in that area of policy, they're not experts in government. Most people are ****ty readers as well. So like, you have a reporter who has spent 10 years writing about this stuff. Or you have yourself who has spent 15 minutes reading a couple of two page articles. We're completely unqualified to render a judgment. We're basically just reinforcing our own internal biases when we decide which side to believe.
I agree with all of that apart from the "get annoyed by scientists and media" part. You should be annoyed at scientists and media because they report the straight line without caveats for an agenda.
So thus we have one side that will claim "more forest cover" and the other side that will claim "forest being cut down." The caveat that you are explaining is not given light. Scientists in this age are not immune to politics and very often are quite happy to just play along with the narrative that is being used. That allied with journalists just wanting a scientist or academic to give them a "creditable" yes answer to their story's narrative.
This is the same for all sorts of subject matter. And thus we have (example) one article from the Mail that says "X is not true" and one article from the Guardian that says "X is true" and the reality is that what they are detailing is true but the point that it does not confirm the actual point they are using the data to say is true.
There are arguments online that the icecaps are growing from deniers. We have articles in other areas that say they are reducing. I can't remember which way round it is but the 2 sides are using data where it is either increasing or decreasing in area while the other side are talking about volume/depth. So this example might be the wrong way round but just for example. One side is saying the icecaps are decreasing because they aren't as thick while the other side are saying they aren't decreasing because they are taking up more area.
This is one reason why I like John Curtice and Matthew Goodwin's analysis on politics and polls because they don't just play along. They will state what the result is but make clear caveats of why that is or what it means while all the others are quite happy to agree with the narrative being used.
We are in an era of headlines and small print where the public are even less inclined to read the actual story let alone the small print. Headline and first paragraph and on to the next thing.