Wondrous wetland crucial currents: a journey on Chile's Cruces River reveals a long-protected sanctuary where tranquil waters may meet a disturbing future.

• Author: Stuparich, Ricardo Carrasco

The serpentine tongue of the Cruces River becomes visible from the air a few minutes after take-off from the city of Valdivia. At first glance it appears lifeless only a dismembered extension of flooded marshlands. But as you move closer, the crisp, clean air that, precedes the characteristic southern rainstorms allows a clear view of the life in these great wetlands. Details appear slowly. If you look closely, you can see hundreds of black-necked swans, small white spots on the water. Herons cross from one shore to another in sleepy flight, stopping occasionally to rest on a branch. A rowboat from the village of Punucapa etches a fine trail through the placid waters.

The Cruces River Nature Sanctuary, or Carlos Anwandter Sanctuary, is fifteen miles long and just over a mile wide, with a total surface area of more than twelve thousand acres. Over the years it has become refuge for more than ninety species of birds, numerous mammals, fish, and insects, and an impressive number of colorful wildflowers. Native forest is still untouched in some areas.

The site of ocean deposits and sediments since the Tertiary Period, the Cruces River basin has a temperate, warm climate, with a dry season of less than four months, making it an ideal place for many aquatic birds. Precipitation levels can reach nearly eighty inches a year. May, June, and July are the wettest months, making the winter seem it interminable and the arrival of spring a blessing.

As I snap some photos through the window of the small plane, the pilot mentions that the last time he flew over the area on what was otherwise a completely clear day, he had gotten lost for a few minutes in a dense layer of clouds formed by evaporation from the Valdivian rain forest. These clouds penetrate the inner valleys, crouching low around Oncol Peak, the highest peak of the coastal mountain range at 2,460 feel above sea level. In the Mapuche language oncol means steep mountain, and the rain forest here is home to a wealth of trees, like the giant coigues, robles, maitines, olivillos, ulmos, lumas, pitras, and arrayanes, to name just a few.

But the diversity of fauna is best appreciated from the water, and a kayak is ideal for moving smoothly and silently among the abundant aquatic plants. We set out from the historic San Luis de Alba Fort--two hours north of the city of Valdivia. It turns out to be a good place to begin our journey. Leaving the fort behind, we paddle through a narrow corridor lined by willows. The soft current takes us slowly toward the place where the...