Mangrove forest in Phang Nga Bay, Andaman Sea, Thailand

© Ratnakorn Piyasirisorost/Getty Image

In the tropics, land greets sea warmly. International Day of the Tropics

Only in the tropics do forests grow in salt water. Take this forest of mangrove trees in Phang Nga Bay in southern Thailand, one of the largest and best-preserved mangrove forests in the country. Adapted to thrive in coastal marshes and swamps, mangroves can filter salt water and withstand strong coastal storms. Virtually all mangrove forests and all species of mangrove grow only in the tropical regions of the world. They are protectors of the coastlines, acting as a buffer against storms and floods.

Today and on every June 29, we join the United Nations in marking the International Day of the Tropics, a moment to focus on the unique beauty of this part of the world and the challenges faced here. The tropics are roughly defined as the area above and below the equator between the Tropic of Cancer and the Tropic of Capricorn. By 2050, the UN estimates the tropics will be home to most of the humans on Earth, and two-thirds of the world's children. The tropics are also home to the poorest parts of our world and those most vulnerable to global warming.

Phang Nga Bay on the Andaman Sea is one of the most treasured and visited sites in Thailand. The south-facing bay is about 150 square miles in size, and contains numerous limestone islets, tower karsts, cliffs, caves, and lagoons. At its mouth is the tourist mecca of Phuket Island. Much of the bay is protected as the Ao Phang Nga National Park, created in 1981 by royal decree. The most famous landmark in the park is probably Ko Tapu, a tall, cylindrical rock that is narrower at its base than at its top. It was featured in the 1974 James Bond movie 'The Man with the Golden Gun,' and has since been dubbed 'James Bond Island.' The real star of Phang Nga, however, is the mangrove. Resilient, wondrous, and beautiful, mangroves are an apt metaphor for the tropics they inhabit.