Dispute over precision with coauthor
Just because you have the additional digits, doesn't mean you should report them.

Accuracy and precision are extremely important concepts in the reporting of scientific data. Excessive precision, as you suggest, implies too much reliability in the accuracy of scientific data. For instance, someone turned in a report to me saying that a particular parameter was known to be:


  E = 1.3405987423423 GPa


If this were to be published in a paper, it could be rejected out of hand for incompetence, because the parameter E is often known only to one or two decimal places, let alone four. 

In general, you need to make your reporting consistent with the assumptions and the accuracy of the measurement techniques. One way to figure this out is to note the accuracy of your measurement—what is the expected error in the measurement? If the error in your measurement technique is, for instance, plus or minus 1 global hectare, then by all means report it to the nearest hectare. If it's plus or minus 1000, though, reporting to the nearest hectare will look quite silly.

How do you deal with this? (I've actually had to do something like this before. Similar argument, but not exactly the same.) In this particular instance, engaging in a little hyperbole might be useful. Instead of reporting it to four significant digits, show him a version of the text that lists the data to the full precision you have available—something clearly ridiculous that reports things down to six or seven decimal places, if possible. Then, when he argues that what you're doing doesn't make sense, you can argue "what's the harm in reporting extra digits?" That should be enough to have your coauthor "see the light."