in one hand a tea garden is not a forest, i mean wild one. parameters
applied to forests can be not the same. in a garden the evolution is
stopped and manipulated by humans, although a tea garden seems to be
part of nature, in fact it is not, at least completely. so talking
about lost of diversity, maybe has another meaning than if you talk
about forest. maybe the question is, are there still wild plants of
camelia sinensis? does exit a virgin forest of camelia sinensis?

in other hand, biodiversity in crops also has been decreasing along the
20th century, the traditional varieties disappeared as global market of
seeds grew. for example in spain [i guess in other mediterranean
countries] there was to be used a rye class with long long canes, they
were used to make many kinds of baskets, and as seeds were not
'prepared' some of them used to have a very poisonous fungus called in
spanish 'cornezuelo del centeno' [Claviceps purpurea], quite common in
cereals, and more in rye, that was collected by hand, because was very
useful in chemistry, and was well paid. now cereals are all treated to
avoid this kind of things, and life is quite easier, but the seeds are
only one kind, don't know exactly the number of different varieties in
cereals, but the point is that the number has decreased, and as in
nature, variety has many advantages or pros. i heard anyone not much
time ago that those fields of cereals with long canes rocked by the
wind in castilla talked by poets will be only just a memory [i didn't
even heard of this long canes ...]

this was only an example, i guess is the same with any other crop. only
few very very local crops has been developed from traditional seeds,
but only because no big multinational factories were interested in
production of these seeds, i guess.

in wine cultivation, the ancient indigenous plants are much more
valuable than clonal, that 'only' are used to make the plant alive, but
the grapes are from ancient clones [in this lands that are still
preserved from those past epidemics] to give the wine a particular
taste. there are wine labels that only want to produce bottles and
bottles with an easy standard taste, and others that want to be
different, to be traditional, let's say respectful with their relatives
[it's a way of talking] and achieve something that has, let's say, more
layers than only a correct product... i think with tea must be
something similar, not only producing, but a particular care

regards from madrid,
bonifacio barrio hijosa
http://worldoftea.webcindario.com/
....site in progress