Climate change and agriculture are interrelated processes, both of which
take place on a global scale. Climate change affects agriculture in a number
of ways, including through changes in average temperatures, rainfall, and
climate extremes; changes in pests and diseases; changes in atmospheric carbon
dioxide and ground-level ozone concentrations; changes in the
nutritional quality of some foods; and changes in sea level.
Climate change is already affecting agriculture, with effects unevenly
distributed across the world. Future climate change will likely negatively
affect crop production in low latitude countries, while effects in northern
latitudes may be positive or negative. Climate change will probably increase
the risk of food insecurity for some vulnerable groups, such as the poor.
Agriculture contributes to climate change by anthropogenic emissions of
greenhouse gases, and by the conversion of non-agricultural land into
agricultural land. Agriculture, forestry and land-use change contributed around
20 to 25% to global annual emissions in 2010.
There are range of policies that can reduce the risk of negative climate
change impacts on agriculture, and to reduce GHG emissions from the
agriculture sector. Impact of climate change on agriculture
Despite technological advances, such as improved varieties, genetically modified
organisms, and irrigation systems, weather is still a key factor in
agricultural productivity, as well as soil properties and natural communities.
The effect of climate on agriculture is related to variabilities in local
climates rather than in global climate patterns. The Earth's average surface
temperature has increased by 1.5 °F since 1880. Consequently, agronomists
consider any assessment has to be individually consider each local area.
On the other hand, agricultural trade has grown in recent years, and now
provides significant amounts of food, on a national level to major importing
countries, as well as comfortable income to exporting ones. The international
aspect of trade and security in terms of food implies the need to also consider
the effects of climate change on a global scale.
A study published in Science suggests that, due to climate change, "southern
Africa could lose more than 30% of its main crop, maize, by 2030. In South Asia
losses of many regional staples, such as rice, millet and maize could top 10%".
The Intergovernmental Panel on Climate Change has produced several reports that
have assessed the scientific literature on climate change. The IPCC Third
Assessment Report, published in 2001, concluded that the poorest countries
would be hardest hit, with reductions in crop yields in most tropical and
sub-tropical regions due to decreased water availability, and new or changed
insect pest incidence. In Africa and Latin America many rainfed crops are
near their maximum temperature tolerance, so that yields are likely to
fall sharply for even small climate changes; falls in agricultural
productivity of up to 30% over the 21st century are projected. Marine life and
the fishing industry will also be severely affected in some places.
Climate change induced by increasing greenhouse gases is likely to affect
crops differently from region to region. For example, average crop yield is
expected to drop down to 50% in Pakistan according to the UKMO scenario whereas
corn production in Europe is expected to grow up to 25% in optimum hydrologic
conditions. More favourable effects on yield tend to
depend to a large extent on realization of the potentially beneficial effects of
carbon dioxide on crop growth and increase of efficiency in water use.
Decrease in potential yields is likely to be caused by shortening of the
growing period, decrease in water availability and poor vernalization.
In the long run, the climatic change could affect agriculture in several ways
productivity, in terms of quantity and quality of crops
agricultural practices, through changes of water use and agricultural inputs
such as herbicides, insecticides and fertilizers
environmental effects, in particular in relation of frequency and intensity of
soil drainage, soil erosion, reduction of crop diversity
rural space, through the loss and gain of cultivated lands, land speculation,
land renunciation, and hydraulic amenities.
adaptation, organisms may become more or less competitive, as well as humans may
develop urgency to develop more competitive organisms, such as flood
resistant or salt resistant varieties of rice.
They are large uncertainties to uncover, particularly because there is lack of
information on many specific local regions, and include the uncertainties
on magnitude of climate change, the effects of technological changes on
productivity, global food demands, and the numerous possibilities of
adaptation. Most agronomists believe that
agricultural production will be mostly affected by the severity and pace of
climate change, not so much by gradual trends in climate. If change is gradual,
there may be enough time for biota adjustment. Rapid climate change,
however, could harm agriculture in many countries, especially those that are
already suffering from rather poor soil and climate conditions, because there is
less time for optimum natural selection and adaption.
But much remains unknown about exactly how climate change may affect farming
and food security, in part because the role of farmer behaviour is poorly
captured by crop-climate models. For instance, Evan Fraser, a geographer at
the University of Guelph in Ontario Canada, has conducted a number of
studies that show that the socio-economic context of farming may
play a huge role in determining whether a drought has a major, or an
insignificant impact on crop production. In some cases, it seems that even minor
droughts have big impacts on food security, versus cases where even
relatively large weather-related problems were adapted to without much
hardship. Evan Fraser combines socio-economic models along with
climatic models to identify “vulnerability hotspots” One such study
has identified US maize production as particularly vulnerable to climate
change because it is expected to be exposed to worse droughts, but it does
not have the socio-economic conditions that suggest farmers will adapt to these
changing conditions. = Observed impacts =
So far, the effects of regional climate change on agriculture have been
relatively limited. Changes in crop phenology provide important evidence of
the response to recent regional climate change. Phenology is the study of
natural phenomena that recur periodically, and how these phenomena
relate to climate and seasonal changes. A significant advance in phenology has
been observed for agriculture and forestry in large parts of the Northern
Hemisphere. Droughts have been occurring more
frequently because of global warming and they are expected to become more
frequent and intense in Africa, southern Europe, the Middle East, most of the
Americas, Australia, and Southeast Asia. Their impacts are aggravated because of
increased water demand, population growth, urban expansion, and
environmental protection efforts in many areas. Droughts result in crop failures
and the loss of pasture grazing land for livestock.
= Projections = As part of the IPCC's Fourth Assessment
Report, Schneider et al. projected the potential future effects of climate
change on agriculture. With low to medium confidence, they concluded that
for about a 1 to 3 °C global mean temperature increase there would be
productivity decreases for some cereals in low latitudes, and productivity
increases in high latitudes. In the IPCC Fourth Assessment Report, "low
confidence" means that a particular finding has about a 2 out of 10 chance
of being correct, based on expert judgement. "Medium confidence" has about
a 5 out of 10 chance of being correct. Over the same time period, with medium
confidence, global production potential was projected to:
increase up to around 3 °C, very likely decrease above about 3 °C.
Most of the studies on global agriculture assessed by Schneider et al.
had not incorporated a number of critical factors, including changes in
extreme events, or the spread of pests and diseases. Studies had also not
considered the development of specific practices or technologies to aid
adaptation to climate change. The US National Research Council
assessed the literature on the effects of climate change on crop yields. US NRC
stressed the uncertainties in their projections of changes in crop yields.
Their central estimates of changes in crop yields are shown above. Actual
changes in yields may be above or below these central estimates. US NRC also
provided an estimated the "likely" range of changes in yields. "Likely" means a
greater than 67% chance of being correct, based on expert judgement. The
likely ranges are summarized in the image descriptions of the two graphs.
Food security The IPCC Fourth Assessment Report also
describes the impact of climate change on food security. Projections suggested
that there could be large decreases in hunger globally by 2080, compared to the
2006 level. Reductions in hunger were driven by projected social and economic
development. For reference, the Food and Agriculture Organization has estimated
that in 2006, the number of people undernourished globally was 820 million.
Three scenarios without climate change projected 100-130 million undernourished
by the year 2080, while another scenario without climate change projected 770
million undernourished. Based on an expert assessment of all of the
evidence, these projections were thought to have about a 5-in-10 chance of being
correct. The same set of greenhouse gas and
socio-economic scenarios were also used in projections that included the effects
of climate change. Including climate change, three scenarios projected
100-380 million undernourished by the year 2080, while another scenario with
climate change projected 740-1,300 million undernourished. These
projections were thought to have between a 2-in-10 and 5-in-10 chance of being
correct. Projections also suggested regional
changes in the global distribution of hunger. By 2080, sub-Saharan Africa may
overtake Asia as the world's most food-insecure region. This is mainly due
to projected social and economic changes, rather than climate change.
Individual studies Cline looked at how climate change might
affect agricultural productivity in the 2080s. His study assumes that no efforts
are made to reduce anthropogenic greenhouse gas emissions, leading to
global warming of 3.3 °C above the pre-industrial level. He concluded that
global agricultural productivity could be negatively affected by climate
change, with the worst effects in developing countries.
Lobell et al. assessed how climate change might affect 12 food-insecure
regions in 2030. The purpose of their analysis was to assess where adaptation
measures to climate change should be prioritized. They found that without
sufficient adaptation measures, South Asia and South Africa would likely
suffer negative impacts on several crops which are important to large food
insecure human populations. Battisti and Naylor looked at how
increased seasonal temperatures might affect agricultural productivity.
Projections by the IPCC suggest that with climate change, high seasonal
temperatures will become widespread, with the likelihood of extreme
temperatures increasing through the second-half of the 21st century.
Battisti and Naylor concluded that such changes could have very serious effects
on agriculture, particularly in the tropics. They suggest that major,
near-term, investments in adaptation measures could reduce these risks.
"Climate change merely increases the urgency of reforming trade policies to
ensure that global food security needs are met" said C. Bellmann, ICTSD
Programmes Director. A 2009 ICTSD-IPC study by Jodie Keane suggests that
climate change could cause farm output in sub-Saharan Africa to decrease by 12
percent by 2080 - although in some African countries this figure could be
as much as 60 percent, with agricultural exports declining by up to one fifth in
others. Adapting to climate change could cost the agriculture sector $14bn
globally a year, the study finds. = Regional =
Africa In Africa, IPCC projected that climate
variability and change would severely compromise agricultural production and
access to food. This projection was assigned "high confidence."
Africa's geography makes it particularly vulnerable to climate change, and
seventy per cent of the population rely on rain-fed agriculture for their
livelihoods. Tanzania's official report on climate change suggests that the
areas that usually get two rainfalls in the year will probably get more, and
those that get only one rainy season will get far less. The net result is
expected to be that 33% less maize—the country's staple crop—will be grown.
Asia In East and Southeast Asia, IPCC
projected that crop yields could increase up to 20% by the mid-21st
century. In Central and South Asia, projections suggested that yields might
decrease by up to 30%, over the same time period. These projections were
assigned "medium confidence." Taken together, the risk of hunger was
projected to remain very high in several developing countries.
More detailed analysis of rice yields by the International Rice Research
Institute forecast 20% reduction in yields over the region per degree
Celsius of temperature rise. Rice becomes sterile if exposed to
temperatures above 35 degrees for more than one hour during flowering and
consequently produces no grain. A 2013 study by the International Crops
Research Institute for the Semi-Arid Tropics aimed to find science-based,
pro-poor approaches and techniques that would enable Asia's agricultural systems
to cope with climate change, while benefitting poor and vulnerable farmers.
The study's recommendations ranged from improving the use of climate information
in local planning and strengthening weather-based agro-advisory services, to
stimulating diversification of rural household incomes and providing
incentives to farmers to adopt natural resource conservation measures to
enhance forest cover, replenish groundwater and use renewable energy. A
2014 study found that warming had increased maize yields in the
Heilongjiang region of China had increased by between 7 and 17% per
decade as a result of rising temperatures.
Australia and New Zealand Hennessy et al.. assessed the literature
for Australia and New Zealand. They concluded that without further
adaptation to climate change, projected impacts would likely be substantial: By
2030, production from agriculture and forestry was projected to decline over
much of southern and eastern Australia, and over parts of eastern New Zealand;
In New Zealand, initial benefits were projected close to major rivers and in
western and southern areas. Hennessy et al.. placed high confidence in these
projections. Europe
With high confidence, IPCC projected that in Southern Europe, climate change
would reduce crop productivity. In Central and Eastern Europe, forest
productivity was expected to decline. In Northern Europe, the initial effect of
climate change was projected to increase crop yields.
Latin America The major agricultural products of Latin
American regions include livestock and grains, such as maize, wheat, soybeans,
and rice. Increased temperatures and altered hydrological cycles are
predicted to translate to shorter growing seasons, overall reduced biomass
production, and lower grain yields. Brazil, Mexico and Argentina alone
contribute 70-90% of the total agricultural production in Latin
America. In these and other dry regions, maize production is expected to
decrease. A study summarizing a number of impact studies of climate change on
agriculture in Latin America indicated that wheat is expected to decrease in
Brazil, Argentina and Uruguay. Livestock, which is the main
agricultural product for parts of Argentina, Uruguay, southern Brazil,
Venezuela, and Colombia is likely to be reduced. Variability in the degree of
production decrease among different regions of Latin America is likely. For
example, one study that estimated future maize production in Latin America
predicted that by 2055 maize in eastern Brazil will have moderate changes while
Venezuela is expected to have drastic decreases.
Suggested potential adaptation strategies to mitigate the impacts of
global warming on agriculture in Latin America include using plant breeding
technologies and installing irrigation infrastructure.
= Climate justice and subsistence farmers in Latin America =
Several studies that investigated the impacts of climate change on agriculture
in Latin America suggest that in the poorer countries of Latin America,
agriculture composes the most important economic sector and the primary form of
sustenance for small farmers. Maize is the only grain still produced as a
sustenance crop on small farms in Latin American nations. Scholars argue that
the projected decrease of this grain and other crops will threaten the welfare
and the economic development of subsistence communities in Latin
America. Food security is of particular concern to rural areas that have weak or
non-existent food markets to rely on in the case food shortages.
According to scholars who considered the environmental justice implications of
climate change, the expected impacts of climate change on subsistence farmers in
Latin America and other developing regions are unjust for two reasons.
First, subsistence farmers in developing countries, including those in Latin
America are disproportionately vulnerable to climate change Second,
these nations were the least responsible for causing the problem of anthropogenic
induced climate. According to researchers John F. Morton
and T. Roberts, disproportionate vulnerability to climate disasters is
socially determined. For example, socioeconomic and policy trends
affecting smallholder and subsistence farmers limit their capacity to adapt to
change. According to W. Baethgen who studied the vulnerability of Latin
American agriculture to climate change, a history of policies and economic
dynamics has negatively impacted rural farmers. During the 1950s and through
the 1980s, high inflation and appreciated real exchange rates reduced
the value of agricultural exports. As a result, farmers in Latin America
received lower prices for their products compared to world market prices.
Following these outcomes, Latin American policies and national crop programs
aimed to stimulate agricultural intensification. These national crop
programs benefitted larger commercial farmers more. In the 1980s and 1990s low
world market prices for cereals and livestock resulted in decreased
agricultural growth and increased rural poverty.
In the book, Fairness in Adaptation to Climate Change, the authors describe the
global injustice of climate change between the rich nations of the north,
who are the most responsible for global warming and the southern poor countries
and minority populations within those countries who are most vulnerable to
climate change impacts. Adaptive planning is challenged by the
difficulty of predicting local scale climate change impacts. An expert that
considered opportunities for climate change adaptation for rural communities
argues that a crucial component to adaptation should include government
efforts to lessen the effects of food shortages and famines. This researcher
also claims that planning for equitable adaptation and agricultural
sustainability will require the engagement of farmers in decision making
processes. North America
A number of studies have been produced which assess the impacts of climate
change on agriculture in North America. The IPCC Fourth Assessment Report of
agricultural impacts in the region cites 26 different studies. With high
confidence, IPCC projected that over the first few decades of this century,
moderate climate change would increase aggregate yields of rain-fed agriculture
by 5–20%, but with important variability among regions. Major challenges were
projected for crops that are near the warm end of their suitable range or
which depend on highly utilized water resources.
Droughts are becoming more frequent and intense in arid and semiarid western
North America as temperatures have been rising, advancing the timing and
magnitude of spring snow melt ﬂoods and reducing river flow volume in summer.
Direct effects of climate change include increased heat and water stress, altered
crop phenology, and disrupted symbiotic interactions. These effects may be
exacerbated by climate changes in river ﬂow, and the combined effects are likely
to reduce the abundance of native trees in favor of non-native herbaceous and
drought-tolerant competitors, reduce the habitat quality for many native animals,
and slow litter decomposition and nutrient cycling. Climate change effects
on human water demand and irrigation may intensify these effects.
United States The US Global Change Research Program
assessed the literature on the impacts of climate change on agriculture in the
United States: Many crops will benefit from increased
atmospheric CO2 concentrations and low levels of warming, but higher levels of
warming will negatively affect growth and yields. Extreme events will likely
reduce crop yields. Weeds. diseases and insect pests benefit
from warming, and will require more attention in regards to pest and weed
control. Increasing CO2 concentrations will
reduce the land's ability to supply adequate livestock feed. Increased heat,
disease, and weather extremes will likely reduce livestock productivity.
According to a paper by Deschenes and Greenstone, predicted increases in
temperature and precipitation will have virtually no effect on the most
important crops in the US. Polar regions
Anisimov et al.. assessed the literature for the polar region. With medium
confidence, they concluded that the benefits of a less severe climate were
dependent on local conditions. One of these benefits was judged to be
increased agricultural and forestry opportunities.
For the Guardian newspaper, Brown reported on how climate change had
affected agriculture in Iceland. Rising temperatures had made the widespread
sowing of barley possible, which had been untenable twenty years ago. Some of
the warming was due to a local effect via ocean currents from the Caribbean,
which had also affected fish stocks. Small islands
In a literature assessment, Mimura et al. concluded that on small islands,
subsistence and commercial agriculture would very likely be adversely affected
by climate change. This projection was assigned "high confidence."
= Poverty impacts = Researchers at the Overseas Development
Institute have investigated the potential impacts climate change could
have on agriculture, and how this would affect attempts at alleviating poverty
in the developing world. They argued that the effects from moderate climate
change are likely to be mixed for developing countries. However, the
vulnerability of the poor in developing countries to short term impacts from
climate change, notably the increased frequency and severity of adverse
weather events is likely to have a negative impact. This, they say, should
be taken into account when defining agricultural policy.
= Mitigation and adaptation in developing countries =
The Intergovernmental Panel on Climate Change has reported that agriculture is
responsible for over a quarter of total global greenhouse gas emissions. Given
that agriculture’s share in global gross domestic product is about 4 percent,
these figures suggest that agriculture is highly greenhouse gas intensive.
Innovative agricultural practices and technologies can play a role in climate
mitigation and adaptation. This adaptation and mitigation potential is
nowhere more pronounced than in developing countries where agricultural
productivity remains low; poverty, vulnerability and food insecurity remain
high; and the direct effects of climate change are expected to be especially
harsh. Creating the necessary agricultural technologies and harnessing
them to enable developing countries to adapt their agricultural systems to
changing climate will require innovations in policy and institutions
as well. In this context, institutions and policies are important at multiple
scales. Travis Lybbert and Daniel Sumner suggest
six policy principles: The best policy and institutional responses will enhance
information flows, incentives and flexibility. Policies and institutions
that promote economic development and reduce poverty will often improve
agricultural adaptation and may also pave the way for more effective climate
change mitigation through agriculture. Business as usual among the world’s poor
is not adequate. Existing technology options must be made more available and
accessible without overlooking complementary capacity and investments.
Adaptation and mitigation in agriculture will require local responses, but
effective policy responses must also reflect global impacts and
inter-linkages. Trade will play a critical role in both mitigation and
adaptation, but will itself be shaped importantly by climate change.
The Agricultural Model Intercomparison and Improvement Project was developed in
2010 to evaluate agricultural models and intercompare their ability to predict
climate impacts. In sub-Saharan Africa and South Asia, South America and East
Asia, AgMIP regional research teams are conducting integrated assessments to
improve understanding of agricultural impacts of climate change at national
and regional scales. Other AgMIP initiatives include global gridded
modeling, data and information technology tool development, simulation
of crop pests and diseases, site-based crop-climate sensitivity studies, and
aggregation and scaling. = Crop development models =
Models for climate behavior are frequently inconclusive. In order to
further study effects of global warming on agriculture, other types of models,
such as crop development models, yield prediction, quantities of water or
fertilizer consumed, can be used. Such models condense the knowledge
accumulated of the climate, soil, and effects observed of the results of
various agricultural practices. They thus could make it possible to test
strategies of adaptation to modifications of the environment.
Because these models are necessarily simplifying natural conditions, it is
not clear whether the results they give will have an in-field reality. However,
some results are partly validated with an increasing number of experimental
results. Other models, such as insect and disease
development models based on climate projections are also used development).
Scenarios are used in order to estimate climate changes effects on crop
development and yield. Each scenario is defined as a set of meteorological
variables, based on generally accepted projections. For example, many models
are running simulations based on doubled carbon dioxide projections, temperatures
raise ranging from 1 °C up to 5 °C, and with rainfall levels an increase or
decrease of 20%. Other parameters may include humidity, wind, and solar
activity. Scenarios of crop models are testing farm-level adaptation, such as
sowing date shift, climate adapted species, irrigation and fertilizer
adaptation, resistance to disease. Most developed models are about wheat, maize,
rice and soybean. = Temperature potential effect on
growing period = Duration of crop growth cycles are above
all, related to temperature. An increase in temperature will speed up
development. In the case of an annual crop, the duration between sowing and
harvesting will shorten. The shortening of such a cycle could have an adverse
effect on productivity because senescence would occur sooner.
= Effect of elevated carbon dioxide on crops =
Carbon dioxide is essential to plant growth. Rising CO2 concentration in the
atmosphere can have both positive and negative consequences.
Increased CO2 is expected to have positive physiological effects by
increasing the rate of photosynthesis. This is known as 'carbon dioxide
fertilisation'. Currently, the amount of carbon dioxide in the atmosphere is 380
parts per million. In comparison, the amount of oxygen is 210,000 ppm. This
means that often plants may be starved of carbon dioxide as the enzyme that
fixes CO2, RuBisCo, also fixes oxygen in the process of photorespiration. The
effects of an increase in carbon dioxide would be higher on C3 crops than on C4
crops, because the former is more susceptible to carbon dioxide shortage.
Studies have shown that increased CO2 leads to fewer stomata developing on
plants which leads to reduced water usage. Under optimum conditions of
temperature and humidity, the yield increase could reach 36%, if the levels
of carbon dioxide are doubled. A study in 2014 posited that CO2 fertilisation
is underestimated due to not explicitly representing CO2 diffusion inside
leaves. Further, few studies have looked at the
impact of elevated carbon dioxide concentrations on whole farming systems.
Most models study the relationship between CO2 and productivity in
isolation from other factors associated with climate change, such as an
increased frequency of extreme weather events, seasonal shifts, and so on.
In 2005, the Royal Society in London concluded that the purported benefits of
elevated carbon dioxide concentrations are "likely to be far lower than
previously estimated when factors such as increasing ground-level ozone are
taken into account." Effect on quality
According to the IPCC's TAR, "The importance of climate change impacts on
grain and forage quality emerges from new research. For rice, the amylose
content of the grain—a major determinant of cooking quality—is increased under
elevated CO2". Cooked rice grain from plants grown in high-CO2 environments
would be firmer than that from today's plants. However, concentrations of iron
and zinc, which are important for human nutrition, would be lower. Moreover, the
protein content of the grain decreases under combined increases of temperature
and CO2. Studies using FACE have shown that increases in CO2 lead to decreased
concentrations of micronutrients in crop plants. This may have knock-on effects
on other parts of ecosystems as herbivores will need to eat more food to
gain the same amount of protein. Studies have shown that higher CO2
levels lead to reduced plant uptake of nitrogen resulting in crops with lower
nutritional value. This would primarily impact on populations in poorer
countries less able to compensate by eating more food, more varied diets, or
possibly taking supplements. Reduced nitrogen content in grazing
plants has also been shown to reduce animal productivity in sheep, which
depend on microbes in their gut to digest plants, which in turn depend on
nitrogen intake. = Agricultural surfaces and climate
changes = Climate change may increase the amount
of arable land in high-latitude region by reduction of the amount of frozen
lands. A 2005 study reports that temperature in Siberia has increased
three degree Celsius in average since 1960. However, reports about the impact
of global warming on Russian agriculture indicate conflicting probable effects :
while they expect a northward extension of farmable lands, they also warn of
possible productivity losses and increased risk of drought.
Sea levels are expected to get up to one meter higher by 2100, though this
projection is disputed. A rise in the sea level would result in an
agricultural land loss, in particular in areas such as South East Asia. Erosion,
submergence of shorelines, salinity of the water table due to the increased sea
levels, could mainly affect agriculture through inundation of low-lying lands.
Low lying areas such as Bangladesh, India and Vietnam will experience major
loss of rice crop if sea levels rise as expected by the end of the century.
Vietnam for example relies heavily on its southern tip, where the Mekong Delta
lies, for rice planting. Any rise in sea level of no more than a meter will drown
several km2 of rice paddies, rendering Vietnam incapable of producing its main
staple and export of rice. = Erosion and fertility =
The warmer atmospheric temperatures observed over the past decades are
expected to lead to a more vigorous hydrological cycle, including more
extreme rainfall events. Erosion and soil degradation is more likely to
occur. Soil fertility would also be affected by global warming. However,
because the ratio of carbon to nitrogen is a constant, a doubling of carbon is
likely to imply a higher storage of nitrogen in soils as nitrates, thus
providing higher fertilizing elements for plants, providing better yields. The
average needs for nitrogen could decrease, and give the opportunity of
changing often costly fertilisation strategies.
Due to the extremes of climate that would result, the increase in
precipitations would probably result in greater risks of erosion, whilst at the
same time providing soil with better hydration, according to the intensity of
the rain. The possible evolution of the organic matter in the soil is a highly
contested issue: while the increase in the temperature would induce a greater
rate in the production of minerals, lessening the soil organic matter
content, the atmospheric CO2 concentration would tend to increase it.
= Potential effects of global climate change on pests, diseases and weeds =
A very important point to consider is that weeds would undergo the same
acceleration of cycle as cultivated crops, and would also benefit from
carbonaceous fertilization. Since most weeds are C3 plants, they are likely to
compete even more than now against C4 crops such as corn. However, on the
other hand, some results make it possible to think that weedkillers could
gain in effectiveness with the temperature increase.
Global warming would cause an increase in rainfall in some areas, which would
lead to an increase of atmospheric humidity and the duration of the wet
seasons. Combined with higher temperatures, these could favor the
development of fungal diseases. Similarly, because of higher
temperatures and humidity, there could be an increased pressure from insects
and disease vectors. = Glacier retreat and disappearance =
The continued retreat of glaciers will have a number of different quantitative
impacts. In the areas that are heavily dependent on water runoff from glaciers
that melt during the warmer summer months, a continuation of the current
retreat will eventually deplete the glacial ice and substantially reduce or
eliminate runoff. A reduction in runoff will affect the ability to irrigate
crops and will reduce summer stream flows necessary to keep dams and
reservoirs replenished. Approximately 2.4 billion people live in
the drainage basin of the Himalayan rivers. India, China, Pakistan,
Afghanistan, Bangladesh, Nepal and Myanmar could experience floods followed
by severe droughts in coming decades. In India alone, the Ganges provides water
for drinking and farming for more than 500 million people. The west coast of
North America, which gets much of its water from glaciers in mountain ranges
such as the Rocky Mountains and Sierra Nevada, also would be affected.
= Ozone and UV-B = Some scientists think agriculture could
be affected by any decrease in stratospheric ozone, which could
increase biologically dangerous ultraviolet radiation B. Excess
ultraviolet radiation B can directly affect plant physiology and cause
massive amounts of mutations, and indirectly through changed pollinator
behavior, though such changes are not simple to quantify. However, it has not
yet been ascertained whether an increase in greenhouse gases would decrease
stratospheric ozone levels. In addition, a possible effect of rising
temperatures is significantly higher levels of ground-level ozone, which
would substantially lower yields. = ENSO effects on agriculture =
ENSO will affect monsoon patterns more intensely in the future as climate
change warms up the ocean's water. Crops that lie on the equatorial belt or under
the tropical Walker circulation, such as rice, will be affected by varying
monsoon patterns and more unpredictable weather. Scheduled planting and
harvesting based on weather patterns will become less effective.
Areas such as Indonesia where the main crop consists of rice will be more
vulnerable to the increased intensity of ENSO effects in the future of climate
change. University of Washington professor, David Battisti, researched
the effects of future ENSO patterns on the Indonesian rice agriculture using
[IPCC]'s 2007 annual report and 20 different logistical models mapping out
climate factors such as wind pressure, sea-level, and humidity, and found that
rice harvest will experience a decrease in yield. Bali and Java, which holds 55%
of the rice yields in Indonesia, will be likely to experience 9–10% probably of
delayed monsoon patterns, which prolongs the hungry season. Normal planting of
rice crops begin in October and harevest by January. However, as climate change
affects ENSO and consequently delays planting, harvesting will be late and in
drier conditions, resulting in less potential yields.
Impact of agriculture on climate change The agricultural sector is a driving
force in the gas emissions and land use effects thought to cause climate change.
In addition to being a significant user of land and consumer of fossil fuel,
agriculture contributes directly to greenhouse gas emissions through
practices such as rice production and the raising of livestock; according to
the Intergovernmental Panel on Climate Change, the three main causes of the
increase in greenhouse gases observed over the past 250 years have been fossil
fuels, land use, and agriculture. = Land use =
Agriculture contributes to greenhouse gas increases through land use in four
main ways: CO2 releases linked to deforestation
Methane releases from rice cultivation Methane releases from enteric
fermentation in cattle Nitrous oxide releases from fertilizer
application Together, these agricultural processes
comprise 54% of methane emissions, roughly 80% of nitrous oxide emissions,
and virtually all carbon dioxide emissions tied to land use.
The planet's major changes to land cover since 1750 have resulted from
deforestation in temperate regions: when forests and woodlands are cleared to
make room for fields and pastures, the albedo of the affected area increases,
which can result in either warming or cooling effects, depending on local
conditions. Deforestation also affects regional carbon reuptake, which can
result in increased concentrations of CO2, the dominant greenhouse gas.
Land-clearing methods such as slash and burn compound these effects by burning
biomatter, which directly releases greenhouse gases and particulate matter
such as soot into the air. Livestock
Livestock and livestock-related activities such as deforestation and
increasingly fuel-intensive farming practices are responsible for over 18%
of human-made greenhouse gas emissions, including:
9% of global carbon dioxide emissions 35–40% of global methane emissions
64% of global nitrous oxide emissions Livestock activities also contribute
disproportionately to land-use effects, since crops such as corn and alfalfa are
cultivated in order to feed the animals. Worldwide, livestock production occupies
70% of all land used for agriculture, or 30% of the land surface of the Earth.
See also Aridification
Biochar Desertification
Environmental issues with agriculture Fisheries and Climate Change
Food security Global warming and wine
International Assessment of Agricultural Science and Technology for Development
addressing the links between climate change & agriculture
Land Allocation Decision Support System – a research tool that is used to test
how climate change may affect agriculture
Retreat of glaciers since 1850 Slash-and-char
Terra preta Water crisis
Climate resilience Notes
References Annex I NC, 6th national communications
from Parties included in Annex I to the Convention including those that are also
Parties to the Kyoto Protocol, United Nations Framework Convention on Climate
Change . Archived 2 August 2014. Battisti, David; Naylor, "Historical
warnings of future food insecurity with unprecedented seasonal heat", Science
323: 240–4, doi:10.1126/science.1164363, PMID 19131626, retrieved 13 April 2012
Cline, W.R., "Global Warming and Agriculture", Finance and Development 45
. Archived 17 August 2014. HLPE, Food security and climate change.
A report by the High Level Panel of Experts on Food Security and Nutrition
of the Committee on World Food Security, Rome, Italy: Food and Agriculture
Organization of the United Nations . Archived 12 December 2014.
Hoffmann, U., ed., Trade and Environment Review 2013: Wake up before it is too
late: Make agriculture truly sustainable now for food security in a changing
climate, Geneva, Switzerland: United Nations Conference on Trade and
Development, ISSN 1810-5432 . Archived 28 November 2014.
IPCC AR5 WG2 A, Field, C.B.,; et al., eds., Climate Change 2014: Impacts,
Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects.
Contribution of Working Group II to the Fifth Assessment Report of the
Intergovernmental Panel on Climate Change, Cambridge University Press .
Also available at IPCC Working Group 2. Archives: Main IPCC website: 16 December
2014; IPCC WG2: 5 November 2014. IPCC AR5 WG3, Edenhofer, O.,; et al.,
eds., Climate Change 2014: Mitigation of Climate Change. Contribution of Working
Group III to the Fifth Assessment Report of the Intergovernmental Panel on
Climate Change, Cambridge University Press . Also available at
mitigation2014.org. Archives: Main IPCC website: 27 November 2014;
mitigation2014.org: 30 December 2014. Lobell, David; Burke, Tebaldi,
Mastrandrea, Falcon, Naylor, "Prioritizing climate change adaptation
needs for food security in 2030", Science 319: 607–10,
doi:10.1126/science.1152339, PMID 18239122, retrieved 13 April 2012 .
Lobell, D.; et al., Prioritizing climate change adaptation needs for food
security - Policy Brief, Center on Food Security and the Environment, Stanford
University CS1 maint: Explicit use of et al.. Archived 27 September 2014.
Non-Annex I NC, Non-Annex I national communications, United Nations Framework
Convention on Climate Change . Archived 13 September 2014.
US NRC, Climate Stabilization Targets: Emissions, Concentrations, and Impacts
over Decades to Millennia, Washington, D.C., USA: National Academies Press
Further reading Fischer G., Shah M. and van Velthuizen
H. "Climate Change and Agricultural Vulnerability". International Institute
for Applied Systems Analysis. Report prepared under UN Institutional Contract
Agreement 1113 for World Summit on Sustainable Development. Laxenburg,
Austria Climate change pushing coffee to
extinction? 17 October 2011 Rosenzweig, Cynthia and Daniel Hillel ed
"Handbook of Climate Change and Agroecosystems: The Agricultural Model
Intercomparison and Improvement Project Integrated Crop and Economic
Assessments. Imperial College Press/ World Scientific Publishing.
External links Climate change on the Food and
Agriculture Organization of the United Nations website.
A comprehensive report on the relationship between climate change,
agriculture and food security by the International Food Policy Research
Institute. See also an overview of IFPRI's climate change research.
Climate Change, Rice and Asian Agriculture: 12 Things to Know Asian
Development Bank LADSS – Climate Change and Agriculture –
Are we asking the right questions? Food Security of Women in the Context of
Climate Change – Online Discussion Forum The Guardian's [climate change coverage
http:www.guardian.co.ukclimate-change] often includes discussions about food
security, including the 30 June 2005 article,One in six countries facing food
shortage How is climate change threatening
agriculture? section of official popularized version of IAASTD synthesis
report Impacts of Climate Change on European
Forests and Options for Adaptation Report to the European Commission
Directorate-General for Agriculture and Rural Development; report written by
European Forest Institute with University of Natural Resources and Life
Sciences, Vienna, Institute of Forest Entomology, Forest Pathology and Forest
Protection, INRA – UMR Biodiversité Gènes et Communautés and Accademia
Italiana di Scienze Forestali) Climate Change and Agriculture in the
ECA region a regional look by the World Bank at climate change and agriculture
in countries in Europe and Central Asia. Climate Change, Agriculture and Food
Security Global scientific research program that seeks to overcome the
threats to agriculture and food security in a changing climate, exploring new
ways of helping vulnerable rural communities adjust to global changes in
climate. Meat Eater's Guide to Climate Change +
Health Life-cycle assessment of greenhouse gas emissions associated with
20 types of meat, fish, dairy and vegetable proteins, as well as these
foods’ effects on health. Climate | Farming First