This situation is very well studied out here (more in relation to birds, indigenous marsupials, small mammals, native rodents, and biodiversity).
Britain has many times the fertility that we do, but the same drivers apply:-
* clearing, fragmentation
* structure simplification (ie 'cleaning' up the mess - usually by burning)
* exotic flora
* industrial agriculture, attendant hybridized sterile seed cycle (owned by monopoly corporations) and the chemical system (artificially fertilized growing, and poisoning killing of natural competition and spent crops) they have been evolved for (particularly GMO)
* destroyed and degraded hydrological and soil building cycles.
Given enough time, these undesirable process could turn even British landscapes into 'virtual' deserts (copious rainfall probably the only saving grace - though do not underestimate the drying effects of wetland and riparian destruction, erosion, and the resultant warming of the climate this brings ).
A couple of fantastic researchers here have spent a lifetime studying some of these components.
Dr. Sue McIntyre:
http://www.gang-gang-gundaroo.com/
http://www.researcherid.com/rid/F-1885-2010
https://mulligansflat.org.au/
https://www.publish.csiro.au/book/4749/
Prof. David Lindenmayer
https://scholar.google.com.au/citations?user=4a2XbLwAAAAJ&hl=en
At a guess, I'd imagine that Britain with its strong history of Natural Sciences, also has its own resident academic luminaries ...... (not forgetting the wonderful Sir David Attenborough
And of course our own maverick and guru - Peter Andrews (OAM) - founder of Natural Sequence Farming
https://www.birdforum.net/showthread.php?t=342128
Chosun :gh: