That first link didn't work for me. I found the page you refer to here: <
https://www.sciencedaily.com/releases/2016/06/160608120736.htm>.
The article itself is located here: <
http://www.ecologyandsociety.org/vol20/iss4/art39/>. I think that the study was limited by its methodology, which the authors describe as follows:
" The survey was only available in English. We solicited respondents through a variety of electronic and social media, including regional, national, and international permaculture-related email lists and online forums, through permaculture interest groups on social media, and through the researcher’s website. We also asked respondents to refer the survey within their own networks. We invited people who “participated in permaculture in any way” to respond, and the survey was restricted to respondents 18 years of age and older. A total of 1055 respondents began the survey. By virtue of web access and language, our sample excludes important sectors of participants in permaculture, and this exploratory study pertains only to that sector of the permaculture network with web access and facility in English."
In other words, agriculturalists in places where English isn't a primary language (i.e., most of the world) were excluded unless they are educated
enough to be perusing foreign-language social media. Those in places like Europe, where English is a primary language (the main working language of the EU, for instance) and social media ubiquitous, were included.
Relying on "electronic and social media" means that people who didn't happen to know the researchers, or have connections to the researchers, or who the researchers located were excluded. The end result was that the researchers got in touch with people who are like themselves, not those who are unlike them.
So, some thoughts:
First, the goal of involving less represented and structurally disempowered groups in permaculture is laudable. That much more remains to be done is obvious. That's basically the case for all aspects of the environmental movements. Much of that involvement may take the form of we permaculture types learning from traditional agriculturalists, not vice versa.
Second, it seems like this particular study's results are not unexpected given its design and designers.
Note: People who speak English are not the whole world.
Finally, if one wants to know what if any impact permaculture is having in the world and who is using its methods, asking about the word "permaculture" on English-language social media is not the way to do it. Going to actual places and seeing actual practices is. That, unfortunately, would be a lot of work and quite resource intensive. But I think it would give better results.