India, Nov. 15 -- I'm perched on the jeep's front seat, whizzing along a narrow road at 5 am. The winter wind lashes at my face, making my eyes water. I pull my cap tighter, wrap my muffler snugly around my neck, and grin. Who celebrates a birthday shivering at dawn in the middle of a tiger reserve? The sharp bite relents when we finally slow down at the park gate. Within minutes, we're inside a forest veiled in delicate morning mist. Tall sal trees stand like sentinels. It's a liquid landscape of silver, green, and gold, the Dudhwa National Park in Uttar Pradesh.

"These Tehri sal forests are part of Dudhwa's larger Terai-Duar ecosystem," our guide explains. This well-drained, slightly elevated soil system is ideal for them to thrive. So...