Over the next 50 years, global population is expected to rise by over 40%, from 7 billion at present to about 10 billion by 2065. If we pursue a “business as usual” approach to CO2 emissions, can we to feed such a massive increase in population? The answer appears to be an emphatic “No”. Even if anthropogenic CO2 emissions were reduced to zero by 2050 (unlikely) the only peaceful alternative to extensive malnutrition, starvation and food wars is to curb CO2 and population growth.
Ongoing anthropogenic emissions have increased the concentration of CO2 in the atmosphere from ~280 ppm in 1750 to almost 396 ppm now and increased the volume absorbed by seawater. The rising level of CO2 in the atmosphere is producing global warming which in turn is causing climate change characterised by increasingly severe and frequent weather events. All of these developments have an effect on our ability to produce, store and distribute food. Some of those effects are beneficial - most are not.
Continued increase in the concentration of CO2 in the atmosphere is having two significant effects on food production. It results in:
Ocean acidification: CO2 entering the atmosphere is largely absorbed by seawater where it forms carbonic acid, reducing the natural alkalinity of the oceans. The rate at which ocean pH is now falling is estimated to be greater than at any time since the Paleocene-Eocene Thermal Maximum.
Calcifying plankton and corals are endangered by this change since increasing acidity dissolves their shells making it more difficult for juveniles to secrete and maintain robust protection. This greatly increases their vulnerability. Many types of fish depend on plankton as their main source of nourishment, consuming them in vast numbers - and on coral reefs for habitat. Their depletion threatens to disrupt the food-chain and significantly reduce fish stocks, a problem exacerbated by overfishing and other forms of ocean pollution.
The massive decline of calcifying plankton will result in major depletion of commercial fish stocks and growing scarcity, even their total loss to those who depend on them most. Millions of humans rely on fish as their main, often their only source of protein.
Plant fertilisation: Elevated CO2 in the atmosphere promotes growth of food crops, particularly the major grain crops (rice, wheat and maize) estimated to increase yields by ~13%, (page 45) significantly less than the expected 40% growth in global population. However, CO2 also stimulates the growth of weeds which compete with food crops for nutrients in the soil. This can be handled by increased use of herbicides, technology better targeting weeds, adding nutrients to the soil and growing crops in a stable climate. Where this occurs the result is likely to be increased crop yield, though possibly with lower nutritional content and higher production (fertilisation) costs putting upward pressure on the cost of food.
The effect of CO2 emissions on average global temperature is a more serious problem. It has resulted in a 0.8°C increase since 1750, most of it occurring in the last 50 years. CO2 emissions are now rising at such a rate that, unless reduced, it is likely average surface temperature will have risen by 2°C by 2050 and at least 3°C by 2100. Global Warming has four major effects on food production, storage and distribution:
1. Reduced crop yield: Raising the level of atmospheric CO2 causes global warming, the latter destabilising climate and reducing crop yield. By stimulating plant growth CO2 also increases demand for nutrients in the soil such as phosphate, potassium and nitrogen. Demand for phosphate is already rising at a time when its availability is contracting while rising soil temperature depletes nitrogen content in the forms which plants can utilise. The outcome: declining food production per capita accompanied by increasing production costs
Food crops have evolved, or been genetically engineered, to produce highest yields where soil and climate conditions are ideal and stable. can be increased by growing crops in the presence of higher atmospheric CO2 concentrations, but only if sufficient nutrients and moisture are available in the soil and temperature remains within limits appropriate for individual crops.
The World Bank Report (pages 44-45) shows that changes to those conditions, particularly temperature and moisture, results in significant decline in yields. While rice yields do not appear to be so severely affected by rising maximum temperature, they are significantly affected by rising minimum temperature brought about by global warming.
2. Loss of agricultural land: Global warming has produced dangerous feedbacks – loss of albedo and increased methane emissions – over which we have no control. This will accelerate future warming and melting of land based ice, particularly polar ice, producing sea level rise. Present indications are that average sea level will rise by at least 1 metre and possibly in excess of 2 metres by 2100, most of it likely to occur in the latter part of the century. Even a 1 metre rise would cause coastal erosion, flood all of the world’s largest river delta’s and in the event of a storm surge, flood and salinate coastal plains.
Warming enables the atmosphere to hold more water producing an increasing number of flood events, washing away top-soil, impairing soil fertility and damaging food crops. Arable land is also removed from agricultural use by urban sprawl (page 38) an effect worsened by projected population increase.
The loss of so much agricultural land, much of it in the most densely populated areas, reduces capacity to produce the food needed to sustain rapidly growing populations. This problem is likely to be worsened by the loss of land now used for grain crops or meat production becoming marginal or unusable for these purposes because of a warmer and more severe climate.
Claims that global warming will open-up land areas in northern Canada and Russia to grain and other food crop production are unlikely to occur, except at the margins. It seems unlikely that stable climate suitable for food crops is going to develop in high latitudes. Further, it can takes a long time for land to develop the biota and nutrients required by such crops. The land north of that currently cropped lacks infrastructure and much of it is affected by permafrost which is seasonally degrading but poorly drained, often producing waterlogged land quite unsuited for agricultural production.
3. Loss of irrigation capacity: Highest food crop yields are obtained by growing crops on irrigated land where moisture can be controlled and optimised. However, capacity to irrigate is dependent on sustainable controlled use of water held in storage and regularly replenished. Three sources of stored water are glaciers, aquifers and dams.
Global warming results in precipitation in the form of rain rather than snow and melting glaciers, most of which are now in retreat. The result is that water is plentiful in winter but in short supply from melting snowpack in spring and summer when it is most needed. This limits the size of crops which can be irrigated from melt water, as evidenced in the Central Valley of California where Sierra Nevada glaciers are all retreating and no longer able to provide the water required for agriculture and burgeoning urban populations.
To maintain agricultural output melt water must now be supplemented by aquifer pumping. However, the rate of pumping required to maintain agricultural output is unsustainable and the aquifer is shrinking. A similar situation exists in north-west India where, in order to maintain food production, it is now necessary to pump aquifers at unsustainable levels. Although there is scope for improved efficiency in the use of water, ultimately a contraction of food production in these areas seems likely.
4. Reduced food safety and storage: Once harvested, food crops must be rapidly delivered to markets if they have a short shelf-life. Grains (from which we obtain half our calorific intake) are stored in local and regional silos until purchased by and supplied to distributers and processers. Grain in silos is subject to loss by consumption and contamination by bacteria, insects and rodents, a problem likely to be exacerbated by a warming climate. Food safety is likely to be adversely affected, particularly in developing countries.
Even in the United States, boasting one of the best developed transport systems in the world, 25% of food produced is lost between harvest and table. Increasing damage to infrastructure due to severe climate events is unavoidable and likely to increase loss of food crops prior to delivery to urban centres.
Most food plants grow in climatic conditions which produce the best yields. They have developed to flourish in a stable, predictable climate. Plants can (like humans) tolerate changes to climatic conditions, provided they do not occur outside known ranges of temperature and moisture and provided that where such changes do occur, they are short-term.
However, an inevitable consequence of global warming is climate change characterised by severe climate including wind events, prolonged droughts, heat-waves and precipitation - either as rain or snow - with fewer cold extremes. The timing and spatial occurrence of these events is largely unpredictable and therefore not yet adequately included in models seeking to describe the effects of climate on food production.
What we do know is that increasingly severe climate events will occur with growing frequency as average temperatures continue to rise and these will adversely affect food production. Recent examples of this are to be seen in:
Events similar to the above all have the effect of reducing food production and increasing its price on the world market. Extreme events are expected to become the norm and grow in severity this century, increasing the damage caused to food crops and, in the latter part of the century, producing scarcity and sharp price increases resulting in regional famine and loss of life.
Increasingly heavy rainfall produces floods of growing severity which, combined with rising sea level cause damage to infrastructure (roads, bridges, railways, port facilities and airports) essential for timely delivery of food crops.
Farm viability can be threatened by the inability of farmers to deliver product because of infrastructure loss. Recent examples of this are seen in road flooding preventing access to dairy farms for the collection of daily milk production. As a result thousands of litres of milk – for which the farmer is not paid - are thrown away because they can not be stored until roads access is restored.
Rapid rise in global population, predicted to be over 10 billion by 2065, with consequential increase in demand for food and water is likely to be accompanied by:
These problems will not occur with immediate severity but will become more marked over the next 87 years, such that well before 2100 demand for food is likely to far outstrip supply.
The socio-economic results will be dire, unless alternatives to business as usual are pursued globally and immediately. Even then, it is possible that mass starvation and loss of life in the latter half of this century will prove unavoidable.
Posted by Riduna on Friday, 5 April, 2013
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