Existence is relative, not absolute.
But you are missing the point..we DONT NORMALLY talk about 'the existence of trees'!
Thats what I call 'seminaritis' or what Wittgenstein might have called
Geschwatz.
'Existence' is a
word we use in social contexts where
utility of concept,like God,
is being negotiated but where participants are unaware of the social construction of 'thinghood'. We don't normally (non philosophically) apply the word to agreed utilities like 'tree'. Using the word 'existence' as a noun, mistakenly in my view, implies 'a state of being' or 'reality' independent of contextual social utility. The concept 'tree' is
useful by virtue of its agreed potential 'properties' as
expected by humans which the word 'tree' triggers. Properties are merely potential interaction events, like 'shade', 'solidity', 'root damage', etc, according to context. The
problem with concepts like 'God', is that there is no agreement about its utility, since its 'properties' are nebulous and parochial....hence believers argue for
the existence of God as though it implied a 'state of being' beyond its social utility....they
want 'existence' to be
a noun whose 'thinghood' is beyond utility considerations, and most atheists who argue to the contrary are also unaware of the of those utility considerations applying to
all humans call 'things'.