Climatic impact on agriculture and food security

Prof Zahurul Karim PhD

The woes
The geographic location and geo-morphological conditions of Bangladesh have made the country one of the most vulnerable ones to climate change (Fig. 1). Floods, droughts, cyclones and tidal surges are common threats. Bangladesh is situated at the interface of two different environments, with the Bay of Bengal to the south and the Himalayas to the north. This peculiar geography of Bangladesh causes not only life-giving monsoons but also catastrophic ravages of natural disasters, to which now are added climate change and SLR. The country has a very low and flat topography, except the northeast and southeast regions. About 10 percent of the country is hardly 1 meter above the Mean Sea Level (MSL), and one-third is under tidal excursions.

Fig. 1 Vulnerability to natural disasters

Source: CEGIS

Our experiences of climatic threats Floods
In an 'average' year, approximately one quarter of the country is inundated. The people living in these areas have adapted by building their houses on raised mounds and adjusting their farming systems. In the past, people here grew low-yielding deepwater rice in the Medium Lowland and Lowland during the monsoon season. Now they mostly cultivate high-yielding rice crops, often using irrigation. Once in every 4 to 5 years, however, there is a severe flood that may cover over 60% of the country and cause loss of life and substantial damage to infrastructure, housing, agriculture and livelihoods. During severe floods, it is the poorest and the most vulnerable ones who suffer most because their houses are often in more exposed locations. Extreme flood frequency has increased in the recent years. In the last 25 years, Bangladesh has experienced six severe floods (Table 1)

Serious floods in the last 25 years
Sources: Government of Bangladesh (2005) National Adaptation Programme, Ministry of Environment and Forests, Dhaka and Government of Bangladesh (2007) 'Consolidated Damage and Loss Assessment, Lessons Learnt from the Flood 2007 and Future Action Plan', Disaster Management Bureau, Dhaka.

Tropical cyclones and storm surges
Cyclone Sidr, 2007
Cyclone Sidr has affected, to various degrees, some 33 out of 64 districts in the country. In total some 8.7 million people have been affected at a time when the country hardly had a chance to recover from devastating floods a few months earlier. The floods alone had affected some 10 million people and took large swathes of precious agricultural land out of production. Table 4 below shows the severity of damages caused by cyclone Sidr in various sub-districts. This closely follows the path of the cyclone (inundation and wind speed) and there is a close correlation between the cyclone path and the damages caused to each of the four sectors. The FAO Mission estimates that up to 70 percent of the Boro season crops, mainly rice and grass pea, were damaged in the severely affected sub-districts and between 20-40 percent in the moderately damaged sub-districts. In addition, crop damages in further 5 districts in the South have also been estimated at about 10 percent of the normal production levels.

A large number of fisher folk lost their fishing gear and houses. The fisher communities usually live on the marginal lands of the coastal areas and were the first to experience the full force of the cyclone.

The government has made an estimate of livestock losses by enumerating the number of losses in most of the affected districts. In five most affected districts some 18 percent of the poultry, 11 percent of goats and sheep, 7 percent of ducks and some 3 percent of the cattle and buffalos have been lost.

In the Sundarbans some 4-5 percent (20 -25 000 ha) of forest area has been severely damaged and nearly 15 percent (60 000 ha) partially damaged. Some alien species, which had been planted in various parts of the Sundarbans on a pilot basis, have been uprooted while in the severely affected areas a large number of trees have been broken from the stem or uprooted. In the partially damaged areas many branches have been broken but the main trunks of the trees are intact. Infrastructure in the Sundarbans and elsewhere in the affected areas has also been damaged.

Furthermore, some 380 km. of embankments have been washed away, which provide much needed protection from annual floods and tidal surges.

Aila, 2009
On May 25th 2009, Cyclone Aila hit 26 districts in the South, affecting a population of around 9 million households (around 3.7 million people). The cultivated land damaged in the area is around 96,617 ha (out of 542,006 ha cultivated in the area); the loss in the production is of around 482,144 MT that is worth of BDT 6,776 million (around 99 M US$) (FAO Mission estimates).

Effects on water availability
Water has become a critical and scarce resource during dry season for irrigated agriculture, domestic and all other uses. Increase in temperature due to climate change will bring a radical transformation in the management of both surface water and groundwater resources. The pressure on water resources intensifies leading to several after-effects which are : water scarcity, reduction in agricultural production, poverty, lack of potable water, sanitation and hygiene problems, decline in groundwater level, water quality deterioration, conflict among users and environmental hazards etc.

The increased evaporative demand due to increased temperature from climate change shall result higher crop water requirements. This will put extra pressure on already dwindling water resources of the country.

About 96% of potable water and nearly 80% of irrigation water is supplied from groundwater. Temporary overdraft or mining conditions occur in many areas of the country due to extensive abstraction of groundwater for mitigating hydrologic droughts especially in dry season. In recent years groundwater levels in many areas, particularly in the north-west region experienced depletion up to 10 m from the static water level for which most of the shallow tube wells (STWs) and Hand Tube wells (HTWs) almost ran dry. Moreover, about 50,000 ponds and ditches have almost dried up. Decline in water levels of these local water bodies are due to interaction of pumping groundwater from the adjacent shallow aquifers and high evaporation losses due to climate change.

Unfortunately, ground water in many places of Bangladesh is not safe and contains variable amount of arsenic. In South Western Bangladesh arsenic level in rice ranges from 0.29 microgram to 0.38 microgram per gram of rice. Much higher concentration is found in leafy vegetables (UNICEF, 2009).

Arsenic problem along with climate change shall further complicate availability of water with large reduction of water during dry season.

Impact of sea level rise
Professor Peter Wadhams (2009) of Cambridge University mentioned that “The summer ice cover will completely vanish in 20 to 30 years but in less than that it will have considerably retreated and in about 10 years, the Arctic ice will be considered as open sea”. Realizing the grave situation the cabinet of Maldives organized an underwater meeting on 18th October, 2009 on the sea floor, 20 feet's below the surface to draw the attention of the world community that the melting of polar ice caps could swamp the Indian Ocean archipelago within a century. This is a great threat not only for Maldives but also for the World.

Sea level rises will lead to submergence of low lying coastal areas and saline water intrusion up coastal rivers and into groundwater aquifers, reducing freshwater availability; damage to the Sundarbans mangrove forest, a World Heritage site with rich biodiversity; and drainage congestion inside coastal polders, which will adversely affect agriculture. Increased river bank erosion and saline water intrusion in coastal areas are likely to displace hundreds of thousands of people who will be forced to migrate, often to slums in Dhaka and other big cities. If sea level rise is higher than currently expected and coastal polders are not strengthened and/or new ones built, six to eight million people could be displaced by 2050 and would have to be resettled. It is now widely believed by experts that sea-level rise by one metre, expected to take place by the current century, will devour the whole of the Sundarbans.

© thedailystar.net, 2010. All Rights Reserved