The figure was published on Monday in the first annual Mekong Delta Economic Report coordinated by the Vietnam Chamber of Commerce and Industry (VCCI) and managed by Fulbright University Vietnam.

The number is alarming considering the number of emigrants in the past decade was larger than the population of some provinces in the delta.

According to the report, the Mekong Delta, with its 17.3 million residents, had zero population growth between 2009 and 2019 compared to the country’s 1.14 percent growth.

Then, in the last two years, its population declined by 0.3 percent.

Experts said people are emigrating mostly due to climate change-related reasons like drought, landslides and pollution but also other factors such as unstable economic structure and poor infrastructure.

Farmers in the delta, the country's rice basket, said floodwaters, which usually come from late July or early August and continue until November or even later with silt from upstream areas have been late or deficient for several years now.

Late last year the highest water levels in the upstream areas of the delta were 1.12-2 meters lower than the long-term average and 1-1.65 meters lower than in 2018.

Dr Vu Thanh Tu Anh, director of the Fulbright School of Public Policy and Management program, said: "The economic opportunities here are limited or unattractive, forcing people to migrate to other regions."

Scholars have projected the delta’s population to fall below 17 million by 2030.

The report also said the economic significance of the region has gradually reduced, with its contribution to the country’s GDP declining steeply from three decades ago.

The delta, which spans more than 3.9 million hectares and has 13 provinces and a city, accounts for 17.7 percent of the country's GDP now.

Experts said it should focus on long-term sustainability instead of immediate benefits, on the market instead of purely production and flexibility instead of being rigid.

It has more than 55,000 businesses.

In 2019 it accounted for 54 percent of the country’s rice output, 70 percent of aquaculture production and 60 percent of fruits.