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Rising Temperatures Melting Away Global Food Security

by Lester R. Brown, Earth Policy Institute

Heat waves clearly can destroy crop harvests. The world saw high heat decimate Russian wheat in 2010. Crop ecologists have found that each 1-degree-Celsius rise in temperature above the optimum can reduce grain harvests by 10 percent. But the indirect effects of higher temperatures on our food supply are no less serious.

Rising temperatures are already melting the West Antarctic and Greenland ice sheets. Recent studies indicate that a combination of melting ice sheets and glaciers, plus the thermal expansion of the ocean as it warms, could raise sea level by up to 6 feet during this century. Yet even a 3-foot rise in sea level would sharply reduce the rice harvest in Asia, a region home to over half the world’s people that grows 90 percent of the world’s rice. It would inundate half the riceland in Bangladesh and submerge part of the Mekong Delta in Viet Nam. Viet Nam, second only to Thailand as a rice exporter, could lose its exportable rice surplus. This would leave the 20 or so countries that import rice from Viet Nam looking elsewhere. Numerous other rice-growing river deltas in Asia would be submerged in varying degrees. 

While the ice sheets are melting, so too are mountain glaciers. The snow and ice masses in the world’s mountain ranges and the water they store are taken for granted simply because they have been there since before agriculture began. Now we risk losing the “reservoirs in the sky” on which so many farmers and cities depend.

The World Glacier Monitoring Service reported in 2010 the nineteenth consecutive year of shrinking mountain glaciers. Glaciers are melting in all of the world’s major mountain ranges, including the Andes, the Rockies, the Alps, the Himalayas, and the Tibetan Plateau.

In South America, some 22 percent of Peru’s glacial endowment, which feeds the many rivers that supply water to farmers and cities in the arid coastal regions, has disappeared. Ohio State University glaciologist Lonnie Thompson reported in 2007 that the Quelccaya Glacier in southern Peru, which had been retreating by 20 feet per year in the 1960s, was retreating by 200 feet annually.  Bolivia is also fast losing the glaciers whose ice melt supplies its farmers and cities with water. Between 1975 and 2006, the area of its glaciers shrank by nearly half. Bolivia’s famed Chacaltaya Glacier, once the site of the world’s highest ski resort, disappeared in 2009.

For the 53 million people living in Peru, Bolivia, and Ecuador, the loss of their mountain glaciers and dry-season river flow threatens food security and political stability. Not only do farmers in the region produce much of their wheat and potatoes with the river water from these disappearing glaciers, but well over half the region’s electricity supply comes from hydroelectric sources. Currently, few countries are being affected by melting mountain glaciers as much as these Andean societies.

As Peru’s glaciers shrink, the water flow from the mountains to the country’s arid coastal region, where 60 percent of the people live, will decline during the dry season. This region includes Lima, which, with nearly 9 million inhabitants, is the world’s second largest desert city, after Cairo. Given the coming decline in its water supply, a U.N. study refers to Lima as “a crisis waiting to happen.”

In many of the world’s agricultural regions, snow is the leading source of irrigation and drinking water. In the southwestern United States, for instance, the Colorado River—the region’s primary source of irrigation water—depends on snowfields in the Rockies for much of its flow. California, in addition to depending heavily on the Colorado, relies on snowmelt from the Sierra Nevada mountain range to supply irrigation water to the Central Valley, the country’s fruit and vegetable basket.

A preliminary analysis of rising temperature effects on three major river systems in the western United States—the Columbia, the Sacramento, and the Colorado—indicates that the winter snow pack in the mountains feeding them will be reduced dramatically and that winter rainfall and flooding will increase. With a business-as-usual energy policy, global climate models project a 70-percent reduction in the snow pack for the western United States by mid-century. A detailed study of the Yakima River Valley, a vast fruit-growing region in Washington State, shows progressively heavier harvest losses as the snow pack shrinks, reducing irrigation water flows.

Agriculture in the Central Asian countries of Afghanistan, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan depends heavily on snowmelt from the Hindu Kush, Pamir, and Tien Shan Mountain ranges for irrigation water. And nearby Iran gets much of its water from the snowmelt in the 5,700-meter-high Alborz Mountains between Tehran and the Caspian Sea.

Ice melting in the Himalayas and on the Tibetan Plateau poses an even graver threat to food security at a global scale. It is the ice melt from these mountain glaciers that helps sustain the major rivers of Asia during the dry season, when irrigation needs are greatest. In the Indus, Ganges, Yellow, and Yangtze River basins, where irrigated agriculture depends heavily on the rivers, the loss of any dry-season flow is bad news for farmers. China is the world’s leading producer of wheat. India is number two. (The United States is number three.) With rice, China and India totally dominate the world harvest. Therefore, the melting of these glaciers coupled with the depletion of aquifers present the most massive threat to food security the world has ever faced.

In India, the giant Gangotri Glacier, which helps keep the Ganges River flowing during the dry season, is retreating. The Ganges River is by far the largest source of surface water irrigation in India and a source of water for the 407 million people living in the Gangetic basin.

Yao Tandong, a leading Chinese glaciologist, reports that glaciers on the Tibetan Plateau in western China are now melting at an accelerating rate. Many smaller glaciers have already disappeared. Yao believes that two thirds of these glaciers could be gone by 2060. If this melting of glaciers continues, Yao says it “will eventually lead to an ecological catastrophe.” The Yangtze, by far the country’s largest river, helps to produce half or more of its 130-million-ton rice harvest.

Like the depletion of aquifers, the melting of glaciers can artificially inflate food production for a short period. At some point, however, as the glaciers shrink and the smaller ones disappear entirely, so does the water available for irrigation.

The melting of the glaciers on the Tibetan Plateau would appear to be China’s problem. It is. But it is also everyone else’s problem. In a world where grain prices have recently climbed to record highs, any disruption of the wheat or rice harvests due to water shortages in India or China will raise their grain imports, driving up food prices for all.

In India, where just over 40 percent of all children under five years of age are underweight and undernourished, hunger will intensify and child mortality will likely climb. For China, a country already struggling to contain food price inflation, there may well be spreading social unrest if food supplies tighten. For U.S. consumers, this melting poses a nightmare scenario. If China enters the world market for massive quantities of grain, as it has already done for soybeans over the last decade, it will necessarily come to the United States—far and away the leading grain exporter.

Ironically, the two countries that are planning to build most of the new coal-fired power plants, China and India, are precisely the ones whose food security is most massively threatened by the carbon emitted from burning coal. It is now in their interest to try and save their mountain glaciers by quickly shifting energy investment from coal-fired power plants into energy efficiency, wind farms, and solar thermal and geothermal power plants.


  1. Says, Who? Studies said? I dont see you posting any references for us to see the study numbers, Global warming is hog wash, everyone knows it, dont put people in panic, this is a article that is not back up with no empirical studies or real research.

  2. Re the previous comment about climate change hogwash – it hardly merits a response, but none the less, pull your head out of your denialist, err, sand.

  3. It’s even much worse than this!!! The world isn’t a globe – this is all a big conspiracy. Global warming is just part of this! There is no such thing as a globe!!! The earth is flat.

  4. Would the primary cause of global warming be an increase in atmospheric CO2, increased solar activity, or is it just a climatic cycle that transpires over the course of a few centuries?

    I doubt coal-fired powerplants will go out of style just yet, especially when it remains as one of the more accessible power generation technologies for developing countries. (Coal is often easier to obtain than petroleum or natural gas.) Increased afforestation to counterbalance increased CO2 output is most desirable. However, afforestation must serve as a way to feed the world’s people as well as to restore the natural environment; human beings are as much as part of nature as any wild creature, whether one lives in the city or in the wilderness.

  5. I recently read something that made much more sense regarding the global food supply than the above political activism.

    “The idea that a change of a few degrees will shrink the world’s farm production reflects the naive thinking of someone who has never been a farmer. If a couple degrees of warming over the next century were the farmers’ biggest problem, they’d be overjoyed”

    Can we also bear in mind the second ethic on these boards, there is no room for the ‘D’ word IMO. A request for references should be met with said references, not name calling, I’m sure we can do better than that.

  6. Hi Ineedscholargyresearch, for references, please check the links within the text (in green).

    It’d be great if, in turn, you could provide references for your statements.

  7. The first link in the piece puts the blame for rising food prices on global warming (a link back to this blog, does that count as evidence?)

    In this link, to the Guardian, they don’t mention global warming, they say ‘we engineered the crisis’

    and in this link (which has historical price graphs from American Journal of Agricultural Economics[i.e. evidence], and happens to be the source for the quote I used) it says the price for the basic foodstuffs corn and wheat did double from 2005 to 2008, and that doubling only returned the price to the 1995 level.

    The OP refers to the Russian heatwave, as if this is linked to global warming, yet NOAA says it was natural variability in it’s peer reviewed piece

    To use the vernacular in the first reply in this thread, the EPI piece seems like ‘hog wash’ to me to.

  8. When it comes to GMO’s and pesticides you guys prove that these international organizations and scientists use faulty science, but when it comes to global warming you take these same peoples’ words as 100% truth. You can’t have it both ways. I am firmly against pesticides and GMO’s for obvious reasons, but I here new things about the climate cycle we are in every day (depending on what new sun cycle we are in, “solar maximum”, and the strength of the ozone layer, and the El Nino and la nina, and who knows what else). Global Warming isn’t “fact”, neither was global cooling, and neither is any broad generalization we choose to describe the climate at one point in time.

  9. Maybe human induced ‘Climate Change’ will come to pass as a whole lot of hogwash. Then again, maybe it won’t. We are gambling with the future wellbeing of generations to come. I imagine myself propped up in a bed, hopefully 40 years from now. If my life energies were spent creating the conditions conducive to life and ‘climate change’ turns out to be hogwash, I could still die peacefully and happily. However, if it turns out to have been a very real thing, I did nothing, leaving my kids and their kids with a broken planet, I would be setting myself up for a very unpleasant death. Are you willing to take that risk?

    p.s. I agree nasty comments get us nowhere. We’re in this together.

  10. Do some people just like the sound of their own voice…

    What would we do without a public forum like the WWW.

    I think there is and always has been a credit-ability issue regarding all information present on the WWW.

    Lester R. Brown is a living legend. “The recipient of 26 honorary degrees and a MacArthur Fellowship, Brown has been described by the Washington Post as “one of the world’s most influential thinkers.”(Wiki)

    All you skeptic’s put together could not equal his credentials.

    ESP those who hide behind WWW persona’s, those who don’t have the guts to sign posts using their real name… Then what a hide to ask for evidence… Just take one look out side you fish bowl. We need to change the way we think…

  11. Brent,

    it may not have occurred to you that atmospheric scientists and those folks who do Monsanto’s R&D at Universities are not “the same people”.

  12. Hi Permaculture people,

    One massive lesson I’ve taken out of the past several years working with producing some of my own food is that the climate is extremely variable. For all sorts of soil reasons, I’m in an area where water can’t be easily stored in dams, it can only be stored in the soil. The only way to sustainably produce a food forest here is to ensure that the soil holds as much water as possible in the first place through various techniques and then to have enough diversity to be able to harvest something even if some crops fail because of weather extremes. When you can’t irrigate and don’t have an industrial agricultural model, you’ll find that every year brings different conditions.

    However, when a culture and systems have developed to rely on a resource that may not be available in the future they may not be able to adapt quickly enough to changes in their environment. This is a massive risk for these food systems irrigated from retreating glaciers. Instead of pursuing traditional irrigation based crops, they may have to diversify radically. The Irish potatoe faminine is an example of where it can go when a population relies too heavily on mono cultures, it exposes a society to shocks of various sorts. There is no alternative to diversification if you and your food production are exposed to a unstable climate.



  13. This is a useful site to explore climate questions:

    The climate system is complex – so our discussion of it will be complex, too, and there is plenty of scope for devious misinformation and doubt-spreading about climate science. We have to avoid going into denial through knee-jerk reactions. For instance, the ‘if all farmers had to worry about was a few degrees of warming’ comment. A few degrees can make the difference between an ice-age, recent conditions, and a ‘hot-house’ earth. A global average change of a few degrees is just that – an average. It means some areas will get much hotter. Farmers in Australia should be very very concerned.

  14. “we’re in this together” great comment Glen :)

    There does seem to be a misunderstanding from some quarters, being sceptical of the CAGW claims does not mean I am sceptical regarding any ecological issue. I just happen to think the scientific literature does not support a high sensitivity to CO2, I happen to think an average rise in global temp of 1.2 – 2 degrees C over the next 100 yrs would be a good thing, especially considering the weather in the next 30 yrs looks set to repeat the cooling period ending in the 1970’s which brought on the Ice age scare of the time.

    The literature supports this view, see this article for the references, which indicate LIA (leaf area index as viewed from satellites) has increased in the last 26 years, the authors say this is due to the last 30yrs warming cycle and increased CO2.

    Since we’re all permaculturists (or at least interested in Permaculture or we wouldn’t be here) I think we should remain vigilant that the original “reasons to act” are not confused with the broad brush of “climate change” the #1 reason to act is soil erosion (by an order of magnitude too), #2 is biodiversity loss, #3 is pollution.

    The broad brush of the “climate change” bandwagon is not required as a reason to act IMO, the proposed solution will not benefit anybody (including the planet) except corporations, governments, and a dozen other subsidy sucking leeches who promote this bandwagon for no other reason than self interest, I really think we should drop it, or at least use articles with some credibility, regardless of the OP authors credibility, the OP is complete rubbish IMO.

    I do however understand those who think otherwise, especially those who might have been introduced to permaculture via this route, but there’s no point wasting each others energy arguing about it, name calling etc. Permaculture is a big bus, and there must be room for everyone, indeed, we ARE in this together ;)

  15. I have noticed a trend in the comments following stories by Brown, McKibben and other thinkers trying to sort through the complexity of anthropomorphic climate change. There is an initial inflammatory remark by some anonymous person or corporate shill that then has the rest of us rallying around, wasting energy saying what we all already know. This is one of those areas of knowledge where it is simple to say “poo!” and difficult to articulate the opposing narrative.
    My brother is an entomologist at UC Berkeley, studying sudden oak death (phytophthora). He can clearly articulate the ongoing demise of America’s great forests, due largely to the introduction of insects and fungi piggy backing on packing crates and horticultural materials from distant lands. The trees (oak, hemlock, elm, ash, cedar, tanoak, sassafras, dogwood, etc.) have little or no resistance. Driving around on a beautiful summer day you’d never know what was going on under the bark. Forests change and climates change. Only humans seem unchangeable.

  16. Pete,

    actually, the scientific literature does not support your view. It only does if one takes on a “I just take into account those articles I like” attitude. The literature quite clearly says that (a) the present rise in CO2 concentrations is a very exceptional phenomenon in the geological history of our planet, and (b) there are strong indications that this probably is a very dangerous thing.

  17. Thanks for taking the time to make these cogent comments Pete. (Since there is no “like” button to click.)

  18. Thankfully permaculture is a big bus – it’s going to have to be! But I don’t agree that ‘the literature supports’ that a degree or two of warming is no great shakes. The planet is now warmer than any time for hundreds of years, possibly 125,000 years, and it is definitely getting warmer. That isn’t in doubt. It is now looking unlikely that we’ll prevent two degrees warming (we’ve already had almost 1), and after two degrees we probably hit tipping points which accelerate warming and take it out of our control (Amazon die back, permafrost releasing methane, arctic ocean absorbing more solar, etc – see ref below).

    Of course we might find theories as to entering cooler sun phases (and it looks like we’d better be!), but let’s not put all our eggs in those baskets. Not when scientists around the world are heaping up worrying evidence on climate change (and no, they are not a conspiracy! Look at the oil funded denialist lobby for that!).

    Your concerns of soil, biodiversity, and pollution are of course all big issues. As it happens, climate change is all of these (caused by pollution, deforestation and soil degradation; threatening to make a third of species extinct this century (see Thomas et al, uni of Leeds); and causing positive feedback mechanisms to further dry out the soil and release its carbon. Unfortunately we can’t solve these (or any issues), without addressing climate change.

    We could bat references around all day – but here’s a few below. My only request is please, don’t discount the problem – if you’re wrong, it’s a serious price to pay. Mass extinction price. And if we act on climate change, we might end up with a greener more pleasant world anyway.

    Ok, I’ve said more than my piece. I’ll shut up now (or try to).

    Allen, M. Et al. (2009). The Exit Strategy. Nature Reports Climate Change: 3; May 2009. Published online.

    Hansen, et al (2008). Target Atmospheric CO2: Where Should Humanity Aim? The Open Atmospheric Science Journal: 2, 217-231.

    Lenton, T. M., Held, H., Kriegler, E., Hall, J.W., Lucht, W., Rahmstorf, S., & Schellnhuber, H. J. (2008). Tipping elements in the Earth’s climate system. Proceedings of the National Academy of Sciences of the USA: 105; 6 (1786-1793).

    Meinshausen, et al. (2009). Greenhouse gas emission targets for limiting global warming to two degrees. Nature (letters): 458; 1158-1163.

  19. The link I provided (further references on that link) shows the last 30yr warming cycle, with increased CO2, increased planetary greening. i.e. it shows the warming and increased CO2 has been a good thing (cold kills more than warm).

    The average temp anomaly (GATA) doesn’t really give us much to quantify in real terms, I think it’s a pretty useless metric scientifically, though very useful for propaganda. Most of the warming has been at night, and is more pronounced in cold regions, and mostly in winter when we actually want it warmer.

    The maximum temp in any given habituated spot on the earth is only a fraction of a degree higher than it was in the 1940’s, the minimum temps are higher, great! Check your local weather stats, look at the max and min temps and check back in the record, we’re lucky in this regard in the UK as we have the CET record, when I observe the differences between now and the 1940’s I remain decidedly unimpressed by the warming, c.30 yr cycles are very apparent, they seem to match ocean cycles, and we appear to be entering a cooling cycle which has me much more worried about the weather we will see for the next 25-30yrs, cold kills, warm is good for the biosphere (see that link, it proves it for the last 26 yrs)

    If we address the major problems facing us (#1,#2,#3 above) we address the concerns of the CAGW hypothesis too, without the carbon taxes, without increased government control of out lives, and without global government, it’s a win win weather CAGW proves to be false or not. If we jump on the CAGW bandwagon we confuse the issues that are important now, not some possible hypothetical dragon in over a century.

    If the last 30yr warming cycle with increased CO2 has been so bad for the biosphere, why is it increasing, why is the Sahara shrinking?

    The evidence shows the OP is based on a false premise, which is why I posted in the first place. Global warming is not responsible for food price increases because the biosphere is growing, it’s more to do with the commodities market being inflated with billions $$$ bailout money IMO.

  20. ScienceDaily (July 12, 2011) — One in 10 species could face extinction by the year 2100 if current climate change impacts continue. This is the result of University of Exeter research, examining studies on the effects of recent climate change on plant and animal species and comparing this with predictions of future declines. –

    @Pete, Sahara is shrinking because of increased evaporation from the Mediterranean Sea. Just like it’s raining like #### in Norway this summer because of warmer surface temperatures in the Atlantic Ocean.

  21. The “no temperature rise since 1998” issue is a persistent myth spread by those who do not know how to do statistics. Everyone who actually has taken a look at the data and can do even just a simple linear regression fit knows first hand it’s not true.

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