Northern Vietnam lowland rain forests

The region is about 380 km from north to south, and about 50 km wide on average. It is bounded by the coast on the east, and the Northern Annamites rain forests to the west. The geological base features extensive limestone ('karst') mountains and valleys. Elevations range from sea level to 1,000 meters, with an average of 88 meters.[3] The primary wet evergreen forest has mostly been cleared in the past by humans; by one estimate only 10% of the original remains.[1]

The climate of the ecoregion is Tropical rainforest climate (Köppen climate classification (Aw)). This climate is characterized as hot, humid, and having at least 60 mm of precipitation every month.[4][5] Annual rainfall increases towards the south, averaging 1,500 mm in the north near Hanoi, and reaching 3,000 mm in the south near Huế. The wet seasons centers on September to January.

The original wet evergreen forest has been mostly broken up by human agriculture and use, and now exists in scattered patches.[1] Over the ecoregion as a whole, only 28% is currently under forest cover; 31% is under agricultural cultivation.[3] The primary forest that exists exhibits a three-tiered canopy rising 25-35 meters. The highest tier is dominated by trees of the Hopea genus, Castanopsis hystrix, and Madhuca pasquieri. A common sub-canopy tree is the Taraw palm (Livistona saribus), used for thatching on huts.

The ecoregion supports some rare animals, including the largest viable population of the critically endangered Northern white-cheeked gibbon (living in Pu Mat National Park), the critically endangered Red-shanked douc, and populations of Gray langurs (a genus of Old world monkey).[1]

Officially protected areas in the ecoregion include:

• Cúc Phương National Park, at the northern end of the region was Vietnam's first national park and still its largest nature reserve.
• Pu Mat National Park, a rugged and remote area of great biodiversity (2,461 plant species identified) on the east slope of the northern Annamite Range.
• Bến En National Park, in the north, is popular with tourists for it large lake (), caves and nature trails.
• Bạch Mã National Park, sitting on steep slopes of granite mountains (to 1,250 meters) near Huế, Bach Ma is in the transition zone between northern and southern Vietnam plant communities.