Do the parcels contain significant oil/gas reserves/rights? Other than that, I could not understand such a drastic increases.
I did go before the county appraisal board once to contest the valuation of my home/property, and was able to get it reduced to a reasonable number. Oddly enough, I had the taxes for other homes on my street that are definitely worth much more than mine, yet were valued at less than mine; however the review board said you can’t use comparisons in your argument --- WTF ?? I said what sense does that make – none. So basically you just have to argue that your house is worth X, and here is why, and lean on them.