Answer:
it is because of the following reasons:
1.To minimize the impact of global environmental problems like global warming, climate change, sea level rise etc.
2. To converse and protect the depleting ecosystem and maintain the balance in the food chain.
3. To protect and conserve the rare and endangered plants and animal species.
4. For creating a healthy and safe working and living environment for good human health.
5. To minimise the impact of climatic disasters like flood, soil erosion, landslide through afforestation and reforestation.