Answer:
Deforestation
Step-by-step explanation:
Deforestation is the primary environmental cost of Southeast Asia's dominance in exports of rubber and palm oil.
Deforestation is the permanent removal of trees to make room for something besides forest and this occurs in the Southern Asia to make room for Rubber and palm oil which are significant in Malaysia, Indonesia, and southern Thailand etc.
Demand for these commodities cause the environmental concerns over deforestation as the main concern in Southern Asia.