(7) This was originally thought to be the result of a lack of vegetation caused by overgrazing and deforestation, but is now thought to be a result of changed temperatures in Earth's oceans caused by global warming.
(This; was thought; T:originally) (This; to be; the result of a lack of vegetation) (Earth's oceans; caused; by global warming) (vegetation; caused; by overgrazing and deforestation) (This; to be; a result of changed temperatures in Earth's oceans)
This This Earth's oceans vegetation This
was thought to be caused caused to be
T:originally
the result of a lack of vegetation
by global warming
by overgrazing and deforestation
a result of changed temperatures in Earth's oceans