All chapters:

Introduction

Climate

Waters and water management

Ecosystems and ecoregions

Species diversity and use of biological resources

Nature conservation: econet and protected areas

Countries & cultures

Economy

Land use

International policy

Once upon a time the whole plain was a huge lake and fine sands were deposited from rivers and lakes throughout the Quaternary period.  These tend to be poorly drained, creating swampy, sometimes saline conditions in the low-lying areas, some of which have boggy peat soils.

Nowadays typical landscapes are flooded meadows and shallow, reed-filled lakes, rivers and old river courses undergoing ecological succession to grassland.  Lakes may be either fresh or brackish, and salt concentrations are increasing in many areas as a result of freshwater diversions for irrigation.  Meadows are dominated by tall grasses that are adapted to flooded soils.  These often grow as dense tussocks that emerge from flooded areas.  Lakes are often filled or lined at the margin by the salt-tolerant reed.  Upland areas are dominated by grasslands, forest-grasslands with crooked elms, and shrub groves of wild-apricot on the hilltops.
During the April-June breeding season, productivity is high, with abundant fish, frogs, mollusks, and aquatic insects, making this an ideal breeding area for waterfowl.  More than 200 bird species have been recorded here, including at least six of the world’s 15 crane species.  The three species that breed here include red-crowned crane (Grus japonensis, IUCN Endangered), white-naped crane (G. vipio, IUCN Vulnerable), and Demoiselle crane (Anthropoides virgo).  Three species stage here prior to migrating to their breeding habitat, the common crane (G. grus) Siberian crane (G. leucogeranus, IUCN Critically Endangered), and hooded crane (G. monacha, IUCN Vulnerable).  Other rare bird species that breed here are Oriental White Stork (Ciconia boyciana, IUCN Endangered), Black-headed Ibis (Threskiornis aethiopicus melanocephalus), Mandarin Duck (Aix galericulata), and Eurasian Spoonbill (Platalea leucorodia).  Common amphibians include toad (Bufo raddei), tree frog (Hyla arborea), frogs (Rana nigromaculata and Rana amurenss).

During the past 100 years the largest grassland-wetland of the Amur-Heilong basin, has been reduced by agriculture and other human encroachment to a series of isolated and shrinking wet grass habitats. There is no reliable regulatory mechanism to ensure sufficient and timely water supply to these remnant wetlands.  This leads to degradation of habitat due to desiccation and agricultural encroachment. 
Numerous nature reserves have been established to protect the remaining Nen River valley wetlands: Zhalong Nature Reserve (2,100 km²), Momoge Nature Reserve (1,440 km²), Xianghai National Nature Reserve, Ke'erqin National Nature Reserve, Tumuji National Nature Reserve (1,000 km²), and others.