Coastal regions face a creeping salinity threat. | New Age
CLIMATE change is commonly described as a long-term shift in average weather patterns, including temperature, rainfall and atmospheric humidity. That definition, while accurate, understates the scale of transformation underway. Climate change is not merely altering seasonal rhythms; it is reshaping the ecological foundations upon which human societies depend. In Bangladesh, one of the most climate-exposed deltaic nations in the world, the crisis is not confined to cyclones, floods or sea-level rise. It extends beneath our feet. Climate change is increasingly a soil crisis.
Climatic variation has existed throughout Earth’s history. Soil formation itself began hundreds of millions of years ago through weathering processes governed by climate, hydrology and biological activity. What distinguishes the present era is not the existence of change, but its unprecedented speed. Anthropogenic greenhouse gas emissions, driven largely by fossil fuel combustion and industrial expansion, have accelerated global warming beyond natural adaptive thresholds. According to recent global estimates, per capita greenhouse gas emissions stood at approximately 6.36 tonnes of CO₂ equivalent in 2022. Bangladesh’s per capita emissions were roughly 1.48 tonnes — substantially below the global average and lower than many least developed countries. Yet low emissions have not shielded the country from disproportionate vulnerability.
The Paris Agreement seeks to limit global temperature rise to well below 2°C above pre-industrial levels, with efforts to remain within 1.5°C. For a low-lying delta with dense population and agrarian dependence, the difference between those thresholds carries profound implications. Climate change is already manifesting not only through extreme events, but through cumulative and structural degradation of land and soil systems.
Soil is a living entity. It sustains biodiversity, regulates water flow, stores carbon and supports crop production. Nearly all human caloric intake originates from land-based ecosystems. Globally, however, up to 40 per cent of land is estimated to be degraded. Over recent decades, significant portions of cropland have been abandoned due to erosion and declining fertility. Tens of billions of tonnes of topsoil are lost annually through mismanagement, extreme rainfall and unsustainable cultivation practices. Bangladesh reflects these global trends, with extensive areas experiencing varying degrees of degradation.
The country’s soils are geologically young and dynamic, shaped primarily by the Ganges – Brahmaputra–Meghna river systems and a monsoon-driven climate. Approximately 80 per cent of the landmass consists of floodplain soils, which underpin rice-based agriculture. Terrace soils, including those of the Barind and Madhupur Tracts, comprise about eight per cent. Hill soils, covering the Chattogram Hill Tracts and parts of Sylhet, account for roughly 12 per cent. Coastal and tidal soils, particularly in districts such as Khulna, Satkhira, Bagerhat, Patuakhali, Barguna and Noakhali, are increasingly affected by salinity.
Sea-level rise constitutes one of the most serious long-term threats to these systems. Globally, mean sea levels rose at an average rate of approximately 1.3 millimetres per year between 1901 and 1971, accelerating to around 3.7 millimetres per year between 2006 and 2018. Thermal expansion of seawater and ice-sheet melt from Greenland and Antarctica are primary drivers. In Bangladesh, relative sea-level trends are compounded by land subsidence. Regional estimates suggest rates significantly higher than global averages in parts of the Ganges tidal floodplain, Meghna estuarine floodplain and Chattogram coastal plain. Much of the southern coastal zone lies between less than one metre and five metres above sea level, amplifying exposure.
Salinity intrusion has therefore intensified. Reduced upstream freshwater flow, tidal inundation and cyclonic storm surges introduce saline water into agricultural lands and aquifers. Salts accumulate within the soil matrix, particularly sodium and chloride ions, disrupting aggregate stability and leading to sodicity. Soil structure deteriorates; infiltration declines; aeration is reduced. Nutrient availability — especially nitrogen and phosphorus — becomes constrained. Microbial communities weaken. Once-productive soils gradually become marginal or unproductive.
Temperature rise compounds these pressures. Bangladesh’s sub-tropical climate already experiences summer maxima between 34°C and 38°C, with historic extremes exceeding 40°C. Average temperatures have increased steadily over recent decades. Higher soil temperatures accelerate organic matter decomposition and increase soil respiration, reducing soil organic carbon stocks. Moisture evaporates more rapidly, intensifying drought stress, particularly in terrace regions such as the Barind Tract. Elevated temperatures also influence chemical reactions within soils, potentially accelerating fertiliser loss and altering nutrient cycles. Crop physiology is directly affected; midday depression of photosynthesis becomes more pronounced under heat stress, reducing productivity.
Rainfall variability introduces additional instability. Annual precipitation ranges from roughly 1,250 millimetres in the western regions to more than 5,000 millimetres in the north-east, with 85–90 per cent occurring during the monsoon. Increasingly erratic onset and withdrawal of rains disrupt cropping calendars. Intense monsoon rainfall accelerates erosion, leaches nutrients and strips topsoil. Larger raindrops physically break down soil aggregates, weakening structure. Flash floods in haor areas deposit sandy sediments over fertile layers, while severe floods mix soil horizons and degrade profile integrity.
Moderate flooding can replenish nutrients through deposition of fresh alluvium. However, extreme floods often cause more harm than benefit. Waterlogging creates anaerobic conditions, depleting oxygen and damaging plant roots. Denitrification under flooded conditions increases nitrogen loss. Altered redox environments affect phosphorus dynamics and micronutrient availability. Riverbank erosion permanently removes productive agricultural land, displacing households and shrinking the cultivable base.
In drought-prone areas such as Rajshahi and Rangpur, increasing frequency of seasonal drought leads to soil moisture deficits, crust formation and reduced biological activity. Hardening of surface layers limits root penetration and reduces water-holding capacity. Over time, such areas become vulnerable to desertification-like processes.
These physical and chemical changes have economic consequences. More than 70 per cent of Bangladesh’s population depends directly or indirectly on agriculture. Soil degradation increases production costs as farmers rely more heavily on chemical fertilisers and pesticides to sustain yields. Excessive chemical input can further degrade soil structure and biological health, creating a cycle of dependency. Declining productivity contributes to rural poverty and encourages migration to urban centres, where displaced populations face precarious living conditions.
Fragile ecosystems — haor wetlands, char lands, coastal belts, hill regions and drought-prone terraces — are particularly exposed. Each represents a distinct interaction between land, water and climate. Climate change disrupts the delicate equilibrium within these systems. Stability and resilience depend on maintaining balance between soil, hydrology and vegetation. When this balance is disturbed by external climatic forces or unsustainable land use, fragility becomes structural rather than episodic.
Policy responses must therefore treat soil sustainability as central to climate adaptation. Bangladesh Agricultural Research Council and international agencies have identified a range of soil-focused strategies. Development of heat-, salinity- and flood-tolerant crop varieties is essential. Restoration of soil organic matter through compost, green manure and retention of crop residues improves structure and water retention. Conservation agriculture and reduced tillage minimise erosion. Improved drainage and raised-bed cultivation can mitigate waterlogging. Crop rotation and integrated soil–water management enhance nutrient cycling. Rainwater harvesting may assist in leaching excess salts from coastal soils. Vegetative riverbank stabilisation can reduce erosion.
These technical measures require institutional support. Climate-smart agriculture programmes must integrate sustainable land management and integrated pest management approaches. Soil testing services and balanced fertilisation initiatives can prevent nutrient imbalance. Ecosystem-based adaptation strategies should be mainstreamed into national planning frameworks. Emerging technologies, including digital soil mapping and remote sensing, offer opportunities for improved monitoring and early warning systems.
However, adaptation cannot depend exclusively on external financing. International climate commitments, including adaptation and loss-and-damage funds, remain uneven in scale and delivery. Domestic governance, research investment and farmer extension services will ultimately determine resilience. Soil protection must be integrated into food security policy, rural development strategy and climate planning.
Climate change in Bangladesh is often narrated through visible disasters — cyclones, tidal surges and catastrophic floods. These events command immediate attention. Soil degradation unfolds more gradually. It does not produce headlines with the same urgency. Yet its consequences are cumulative and enduring. Without healthy soils, agricultural sustainability weakens. Without agricultural sustainability, food security and social stability erode.
The climate challenge confronting Bangladesh is therefore multidimensional. It encompasses atmospheric warming, hydrological shifts and, fundamentally, transformation of the soil systems that sustain life. Protecting soil is not a peripheral environmental objective. It is a strategic imperative.
In the coming decades, Bangladesh’s resilience will depend not only on embankments and cyclone shelters, but on the condition of its floodplains, terraces, hills and coastal lands. Climate policy must extend below the surface. The ground beneath us is changing. Whether it remains productive will depend on decisions taken now.
Dr Md Sohrab Ali is former additional director general of Department of Environment.