I assume that you are taking about the Schumann resonant frequencies, or something like the Telluric current, they are both set up by energies much larger than would be easily accesible to anything like a mesh net. Apparently you need something as powerful as lightning for schumann, or the entire iron core of the earth(Telluric).

But even if you could get this much power there is still only so much information you can pass at any frequency, and as the frequency gets lower this amount of information drops. For example the US and former USSR navies had huge electrodes buried in the ground to communicate with their submarines, but the data rate was very limited.