Yep, that looks like evidence! It certainly seems to be a bit of an issue in what is presumably your neck of the woods, er, fields. That doesn't necessarily equate to a significant issue across the rest of the country, of course. I had a brief search, but couldn't turn up any useful national statistics.

The grubbing up of orchards has been going on for years, I'm afraid. Not always to move away from agriculture, or even from orchards, but farming is a business, and if an orchard can more profitably be turned to something else... And there has also been an issue with the profitability of farming for years, especially for smaller farmers. As for knocking down houses in large gardens, again, that's been known about for years. At least 15 years ago, I can remember reading about this happening on the South coast particularly, in places like Poole. Developer outbids everyone for house with large garden & sea views, knocks down house, builds 6 flats & sells each for the value of the original house & makes millions... Can't say as I like it much, but I can't see what you can do about it.

A similar thing happened on the A10 between Cambridge & Ely, at Waterbeach. One lone house set in a very large plot was allowed to fall into disrepair, presumably whilst planning permission was being sought. Eventually a tall fence was put up which more or less hid the house (I used to drive past it going to / from work), then it disappeared... I've no idea how many houses were put on it in the end. Google is out of date for this also, but if
this link works, it's the lone property where the bus stop is marked. If you go to Satellite, you can see there was a substantial amount of woodland; I don't know how much of that survives; and if you roll down to Streetview, you can see... actually, I think it might be a new property being built. It doesn't look like the old house, which, I'm sure, was further back from the road, and SV reckons that's Aug '16, which is well after the old house went. I have a feeling that this was actually bought up by travellers, which the buildings & caravans that can be seen tends to support.