International Crane Foundation

 
Poyang Lake water levels winter

Yangtze Conservation Story

Yangtze River

In spring five rivers from the south swell with rains as they flow into Poyang Lake, wintering area for the majority of the world’s Siberian Cranes.  In summer, the much larger Yangtze River rises with floods coming from the west, often sending water into the lake.  The water level within the lake basin fluctuates by as much as 11 meters between summer and winter. This scale of change, and the strength of the summer flooding, has prevented development of major parts of this wetland and protected the Siberian Crane’s winter home; however changes caused by dams and other water development projects could alter this delicate system and the future for Siberian Cranes.

Poyang Lake water levels winterPoyang Lake water levels summer

Fluctuating water levels in the Poyang Lake basin between winter (low water, left) and summer (high water, right).

 

ICF In Action

ICF began work at Poyang Lake in 1985. Through surveys of wintering cranes and other waterbirds, we realized how important this area was for Siberian Cranes and other threatened waterbirds and that a long-term research program was needed to understand how wintering waterbirds selected areas for feeding in the lake basin. In the late 1990s, ICF and the Poyang Lake Nature Reserve (PLNR) initiated a project to study the linkages among cranes, water levels, and the aquatic plants that the cranes feed upon during the winter.

While cranes eat of variety of foods in the basin, their primary food is tubers of aquatic plants that the birds dig from the mud with their long, powerful beaks. Cranes need shallow water or soft mud to access their food, as it is difficult or impossible to dig the tubers from dry soil (and they will not wade into water deeper than 30-50 cm to feed). Starting in 1999, ICF has worked with PLNR to collect data on weather and water levels, turbidity (amount of particles in the water), water plant abundance (in the growing season), tuber abundance (in the winter), and bird numbers and distribution.

 

Hooded Cranes, Mike Endres

Wintering White-naped Cranes at Poyang Lake. Photo by Mike Endres/ Little Wing Photo

 

 

Click to enlarge

“ICF and the Poyang Lake Nature Reserve are studying linkages among cranes, water levels, and the aquatic plants that the cranes feed upon during the winter.”

 

Siberian Cranes, Mike Endres

A juvenile (left) and two adult Siberian Cranes in the Poyang Lake basin. Photo by Mike Endres/ Little Wing Photo

 

The Way Forward

What did we learn? We discovered that while cranes depend on shallow waters and wet mud for feeding in winter, they also need suitable water in the summer so that wild celery Vallisneria and other waterplants can grow abundantly. The cranes can only find suitable feeding areas where both these conditions are met in a given year. Thus, our long-term research indicates that fluctuating water levels within the Poyang Lake basin are essential for the survival of Siberian Cranes and other tuber-feeding waterbirds like the vulnerable Swan Geese.

In 2007, ICF began discussions with water resource managers regarding the possible impacts of a dam proposed for the outlet to Poyang Lake. The dam would be open during the high water seasons in the spring and summer but closed during winter to prevent water from dropping below desired levels. Our research indicates that construction of the dam, if it stabilized water levels significantly higher than under natural conditions, could have major, negative impacts on wintering waterbird populations, with the probable loss of extensive feeding areas, along with diversity and flexibility within this major wetland system. We have proposed an approach to lake management, and decision-making about water, that would safeguard the extraordinarily valuable ecosystem services provided by Poyang to millions of people as well as the greatest concentrations of waterbirds in East Asia.  Learn more and download a comprehensive report prepared by ICF and the IUCN SSC Crane Specialist Group on the management of the Poyang Lake wetlands.

Follow ICF researcher, James Burnham, as he tweets from Poyang Lake, China.