Is it walking “in” or “on” the dunes?

I'm trying to do a translation and can't find any example that solves the question; is it walking in or on the dunes?

'Dunes' to the Dutch refers to an area which contains some sandy hills near the sea. The footpath is usually at a lower level, so we'd say 'in' the dunes for walking in the area, instead of 'on' as in on top of a sandy hill.

Solution 1:

Both in the dunes and on the dunes are acceptable.

Another option, possibly better:

Walking among the dunes

Solution 2:

To me, "in" means you're walking amongst and between the dunes, and "on" means actually climbing up and down the piles of sand. If there's a formal footpath designed to avoid most of the up-and-down, I'd probably go with "in" (or "among" as suggested by Zanna's answer). If you want to emphasize the climbing aspect (or maybe damage done to vegetation by straying from designated paths or boardwalks), use "on".

Per Google Ngram, both version see some usage in print with "on" being somewhat more common in recent years, but the n is so low that I'm not sure that's a true trend (and the data from 2000-2008 show "in" as more common). Disaggregating the data and looking at actual examples suggests some evidence for the distinction as I understand it (though I don't think it's a hard-and-fast rule by any means):

Walking in the dunes is discouraged because paths created by walking can widen into large openings between dunes.
—Scott Williams, Corpus Christi, 2009

" . . . We will walk in the dunes, play some games and I will read you a book." . . . The bikes were parked and they started to walk in search of a cozy dip in the dunes that would give some protection from the wind. They soon found the most marvelous spot made just for them. It was a bit grassy as well as sandy right against a hillside—a little dell—large enough for the family.
—Johanna Van Belle-Praamsma, Coram Deo, 2009

They decide to go for a walk in the dunes, with Bernie, too, of course. Amelie learns that dunes are hills of sand, covered in grass and bushes. There are paths leading through them.
—Eva Markert, Amelie Travels to the Seaside, Stories for Little Ones, 2017

With no experience of the coast, I thought it would be possible to walk on the dunes, looking down on the sea and whatever lay behind that tantalizing tangle of wire.
—John Hillaby, A Walk Through Europe, 1977 (snippet view)

During the day, Mark would often watch the tourists (whom the natives called "comers" and "goers") climbing the dunes. Some even walked up during the searing heat of the afternoon. Gramps said, "Anyone walking on the dunes in the blazing noonday sun is crazy. Between the burning sands and the broiling sun, you might as well be turning on a rotisserie."
—Anne Turner Coppola, Ghost Dunes, 2014