Chapter 4 analyses the hazard exposure and vulnerability based on the economic damage (economic vulnerability, Gupta et al., 2010), the number of deaths and missing (social vulnerability, Gupta et al., 2010), according to population criteria, property, livelihoods, energy and industrial activities, settlement and transportation in some provinces and districts (ADB, 2011), and it assesses the vulnerability and risks of areas (Lê Đăng Trung, 2012). 

The exposure to hazards and vulnerability of socio-natural systems in Viet Nam changes in both space and time. It also depends on the danger level of climate extremes, density, value and adaptive capacity of the objects that are exposed to hazards, as well as natural factors such as geology, geomorphology, topography, and hydrology. Climate extremes associated with adverse natural conditions increase the exposure level and vulnerability of human systems and natural ecosystems. Coastal ecosystems, especially mangrove ecosystems and coral are most vulnerable to storm, storm surges and sea level rise, and changes in salinity; terrestrial forest ecosystems are most vulnerable to drought, forest fires, flash floods, mud and rock floods. Vulnerable natural ecosystems can increase the exposure to hazards and reduce the adaptive capacity of human systems.

Climate extremes interacting with each other can mutually strengthen and increase the exposure level and the vulnerability of socio-natural systems. Heavy rains and storm surges cause floods, destroy infrastructure and residential coastal areas, erode sea dikes and mangrove forests, and cause land loss and saltwater intrusion. All of these cause increasingly serious damage to the coastal and lowland areas of Viet Nam, and increases the level of exposure and vulnerability of natural ecosystems and human systems. Human systems can increase exposure (unsuitable water resource use; deforestation; moving to the vulnerable
areas; urbanization; construction of industrial parks in areas, which suffer many climate extremes; living and producing when climate extremes appear frequently; poverty, etc.), or reduce exposure to hazards (enhancing the adaptive capacity of natural-social system; mitigating the negative effects of extreme climates with construction or non-construction solutions such as land use and natural resources planning, which mitigate climate extremes; applying early warning systems; evacuating people out of the affected areas; adjusting production and human activities at the time when climate extremes occur less frequently; living
wisely with climate extremes, etc.), the vulnerability situation, risks and impacts of climate extremes in both natural ecosystems and human systems, and socio-natural systems in general.

Disasters related to weather and climate, and depending on topography can cause significant impact on different areas, sectors and livelihoods, including water resources, agriculture, forestry, fisheries, food systems and food security; natural ecosystems; residential areas, infrastructure and tourism; human health, social protection and social welfare. Over the past 30 years in Viet Nam, the annual average number of people killed or missing due to disasters was about 500, and thousands of people were injured; and economic losses were about 1.5% of GDP, which is 1% higher than that of GDP loss in middle–income countries and about 0.3% higher than losses in low-income countries. From 1989 until now, the number of deaths (social
vulnerability), and the total economic losses (economic vulnerability) caused by disasters in Viet Nam complicated, but overall it tends to increase with GDP growth. Agriculture, including crop farming, livestock, aquaculture and fisheries are vulnerable to climate change. The damages (in cash) of agriculture, irrigation, transport and fisheries caused by natural disasters in Viet Nam

between 1989 and 2009 tended to decrease, but the number of damaged schools, hospitals,etc., tended to increase.The risk of extreme climate extremes differs between the North and the South of Viet Nam, the East and the West, seasonally, and it is increasing due to the change in climatic extremes.Hazard exposure and vulnerability of socio-natural systems will increase in the months and the years in which more climate extremes occur, and will reduce at the time when there are fewer of those events. If the sea level rises by 1 meter, 6.3% of Viet Nam’s land area, approximately 39% of the Mekong River Delta, 10% area of the Red River Delta and Quang Ninh Province, more than 2.5% of the central coastal provinces and more than 20% of Ho Chi Minh City are at risk of flooding (MONRE, 2012).

Exposure and vulnerability often have a complex interaction; and their interaction is complicated at different scales and at different times. The increased level of exposure to hazards of human systems (humans and property, economy, technical and social infrastructure, etc.) and inappropriate human activities are major causes of increased climate risks.