When
trees
are
cut
down
for
wood
or
to
make
space
to
grow
crops
,
we
call
it
____________________
.
When
wind
and
rain
sweep
away
the
soil
and
plants
disappear
,
we
call
it
____________________
.
When
air
,
water
or
soil
are
affected
by
harmful
substances
,
we
call
it
____________________
.
