Climate change and agriculture: Difference between revisions

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Climate change and agriculture may refer to:

This disambiguation page lists articles associated with the title Climate change and agriculture.
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+'''Climate change and agriculture''' may refer to:
-The [[weather]] conditions - [[temperature]], [[radiation]] and [[water]] - determine the [[Carrying capacity|carrying capacity]] of the [[biosphere]] to produce enough [[food]] for the human propulation and domesticated animals. Any short-term fluctuations of the [[climate]] can have dramatic effects on the [[agriculture|agricultural]] productivity. Thus, the climate has a direct incidence on [[food supply]].
+* [[Effects of climate change on agriculture]]
-[[Demography|demographic studies]] indicate that world population growth is expected to slow markedly in the next century, increasing of nearly 3 billion people by 2050. Hence, in the coming years, unless population size is stabilized as soon as possible, [[agriculture]] will have to face an increasing challenge in feeding the [[population explosion|growing population]] of the world.<br>
+* [[Greenhouse gas emissions from agriculture]]
-Many people believe it will also have to face the perspective of global climate changes. A forecasted climate change is [[global warming]], induced by an increasing concentration of radiatively active greenhouse gases.
+{{disambiguation|geo}}
-The appreciation of the effects of potential climatic changes is essential. Many believe it is not until a certain threshold of gravity of the modifications observed, that it will be convenient or pressing to deal with these issues. Agriculture is one of these fields that are carefully monitored.<br>
-Besides, assessment of the '''effect of global climate changes on agriculture''' might help to properly anticipate and adapt farming to limit potential [[food shortage]].
-== Situation at the beginning of the XXI century ==
-=== Assessment on global scale or local scale ? ===
-Despite technological advances, such as [[crop breeding|improved varieties]], [[GMO|genetically modificd organisms]], or [[irrigation]] systems, [[weather]] is still a key factor in agricultural productivity, as well as [[soil]] properties and [[biota|natural communities]]. The effect of climate on agriculture is related to variabilities in climate rather than in global climate patterns. Consequently, agronomists consider it has to be individually considered for each [[ecoregion|local area]].
-On the other hand, agricultural trade has grown in the recents years, and now provides significant national [[food]] amounts to major importing countries, as well as comfortable income to exporting ones. The international aspect of [[food trade]] and [[food security]] implies the need to also consider the effects of [[global climate change|climate change]] on a global scale.
-===Shortage in grain production===
-Between 1996 and 2003, grain production has stabilized slightly over 1800 millions of tons. In 2000, 2001, 2002 and 2003, grain stocks have been dropping, resulting in a global grain harvest short of consumption by 93 millions of tons in 2003.
-The earth's average temperature has been rising since the late 1970s, with the three warmest years on record coming in the last five years.  In 2002, India and the United States suffered sharp harvest reductions because of record temperatures and drought. In 2003 Europe suffered very low rainfall throughout spring and summer, and a record heat damaged most crops from the United Kingdom and France in the west through Ukraine in the east. Bread prices have been rising in several countries in the region. (see [[w:fr:canicule 2003]]).
-== Models and scenarios used to estimate global climate change consequences ==
-=== Climate models limitations ===
-Some major limitations to climate changes consequences estimates are related to the [[climate model|models]] that are being used.
-The ''climate models'' are not really able to give accurate projections because of inadequate understanding of natural processes and computer power limitation. As a consequence, the assessment of possible effects of climate changes are based on estimations. <br>
-Moreover, most models are not able yet to provide reliable projections of changes in climate variability on a local scale, or in frequency of [[extreme weather|exceptional events]] such as storms and drought. For example, there is a lack of consensus among experts in prediction of regional [[soil moisture]] changes.
-=== Crop development models ===
-The study of the effects is using other types of models, such as ''crop development models'', ''yield prediction'', quantities of ''water or fertilizer consumed''. The models condense the knowledge accumulated in influence of the climate, soil, and [[agricultural practices]]. They can make it possible to test strategies of adaptation to the modifications of the environment.
-Because these models are necessarily simplifying natural conditions (often based on the assumption that weeds, disease and insect pest are controlled), 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 types of biological models used ===
-Other models, such as ''insect and disease development'' models based on climate projections are also used (for example simulation of [[aphid]] reproduction or [[septoria]] (cereal fungal disease) development).
-=== Scenarios in biological models ===
-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 [[CO2]] projections, [[temperature]]s raise ranging from 1°C up to 5°C, [[rainfall]] -/+20%. Other parameters may include, [[humidity]], [[wind]], and [[global radiation]].<br>
-Scenarios of crop models are testing farm-level adaptation, such as sowing date shift, climate adapted species ([[vernalisation]] need, heat and cold resistance), [[irrigation]] and fertilizer adaptation, disease resistance.<br>
-Most developed models are about [[wheat]], [[maize]], [[rice]] and [[soybean]].
-== Potential global climate changes consequences on agricultural production ==
-Many scientists position is that '''agricultural shifts are likely'''.
-Several types of changing parameters can have an effect on agriculture
-* a ''direct effect is the composition of the earth atmosphere'' : [[CO2]] and [[ozone]]. Gases such as CH4, NO2 and CFC are commonly believed not to have any effect on physiological processus.
-* some ''indirect effects are climate parameters'' resulting from climate change : [[temperature]], [[insolation]], [[rainfall]], [[humidity]]
-* other ''indirect effects are the side effects due to the climatic changes'' : increase of the [[sea level]], changes in [[Gulf stream|ocean currents]], [[tornado|tornadoes]]...
-All these influences combine negatively or positively :
-* The assessment of these effects is different whether one considers annuals [[crops]] (cereals, leguminous) or herbaceous perennial cultures (fodder, meadows) or other cultures such as vine or fruit trees...
-* The effects are also different depending on the latitude : in temperate countries, effects are found less negative or even rather beneficial, while in tropical and desertic countries they tend to be adverse.
-* Finally, effects depend on altitude, mid and high altitude places rather benefiting from a warmer temperature.
-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 hydric conditions.
-However, the more favourable effects on yield depend to a large extent on realization of the potentially benefiting effects of CO2 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.
-=== Temperature potential effect on growing period ===
-Duration of [[crop growth cycle]]s are above all related to temperature.<br>
-An increase in temperature will speed up development. In the case of an annual crop, the duration between sowing and harvesting will shorten (for example, corn duration cycle could shorten between 1 and 4 weeks). The shortening of the cycle would rather has adverse effect on productivity because of [[senescence]] occurring sooner.<br>
-Temperature changes could also have serious implications for crops and trees that need [[vernalisation]].
-=== Atmospheric CO2 potential effect on yield ===
-[[CO2|carbon dioxide]] is a perfect example of a change that could have both positive and negative consequences.
-* CO2 is expected to have positive physiological effects through [[photosynthesis]] increase. This effect should be higher on [[C3 crops]] (such as wheat) than on [[C4 crops]] (such as corn). Under optimum conditions of temperature and humidity, the yield increase could reach 36 % (for a doubling of CO2).
-* Higher amounts in CO2 will also reduce the loss of water through [[evapotranspiration|transpiration]], hence decreasing the plants need in water.
-* On the other hand, other studies also show a change in harvest quality. The growth improvment in [[C3 plants]] could favor vegetative [[biomass]] on grain biomass; thus leading to a decrease in grain production yield.
-CO2 is believed by many scientists to be potentially responsible of productivity increase : 10-15 % for wheat and soybean, 8% for corn and rice for a +2°C scenario on average. However, these results mask great differences among countries.
-=== Water availability effect on productivity ===
-Water is a major limiting factor in the growth and production of crops worldwide.<br>
-In spite of better water efficiency use, higher summer temperature and lower summer rainfall is likely to have adverse effect. The intensification of the [[water cycle|hydrological global cycle]] will have consequences such as more frequent [[drought]] in northern sub-tropical areas or [[desertification]] extension in arid areas. In developed areas of the world agriculture (and competing industry and municipal users) are mining [[fossil]] water supplies. In coastal areas deep water wells also reverse normal ground water flow toward the ocean, leading to [[saltwater intrusion|saline water intrusion]] into [[aquifers]]. Further increases in usage will accelerate the ''day of reckoning'' when societies must conform ground water usage to actual recharge rates.
-=== Erosion and fertility ===
-[[Soils retrogression and degradation|Soil degradation]] is more likely to occur, and [[soil fertility]] would probably be modified.
-*A soil constant is its [[carbon/nitrogen ratio]]. A doubling of carbon is likely to imply a higher storage of [[nitrogen]] in soils, thus providing higher fertilizing elements for plants, hence better yields. The average needs for nitrogen could decrease, and give the opportunity of changing the [[fertilisation]] strategies.
-* The increase in precipitations would probably result in greater risks of [[erosion]], according to the intensity of the [[rain]].
-* The possible evolution of the [[soil organic matter]] is a very debated point though : while the increase in the temperature would induce a greater [[mineralisation]] (hence lessen the soil organic matter content), the atmospheric CO2 concentration would tend to increase it.
-=== Global climate change potential effect on pests, diseases and weeds ===
-A very important point to consider is that [[weed]]s would undergo the same acceleration of cycle than cultivated crops, and would also benefit of carbonaceous fertilization.<br>
-Most weeds being [[C3 plant]]s, they are likely to compete even more than now against crops such as corn. However some results make it possible to think that [[weedkiller]]s could gain in effectiveness with the temperature increase.
-The increase in rainfall is likely to lead to an increase of atmospheric humidity and maybe to the duration of moisturing.<br> Combined with higher temperatures, these could favor the development of [[fungal disease]]s.
-Similarly, because of higher temperatures and humidity, there could be an increased pressure from [[insect]]s and [[disease vector]]s.
-=== Agricultural surfaces and climate changes ===
-Climate change is likely to increase agricultural land surface near the poles by reduction of frozen lands. Sea levels are expected to get up to one meter higher by 2100, though this projection is disputed. Rise in sea level should result in agricultural land loss in particular in South East Asia. Erosion, submergence of shorelines, [[salinity]] of water table, could mainly affect agriculture through inundation of low-lying lands.
-=== Ozone and UV-B ===
-Some scientists think agriculture could be affected by any decrease in stratospheric [[ozone]], which could increase biologically dangerous [[ultraviolet]] radiation. Excess UV radiation can directly effect plant [[physiology]], and indirectly through changed [[pollinator]] behavior, though such changes are difficult to quantify.
-=== Temporal variability and forecasting of the climate ===
-Many believe the general foreseeability of the climate will decrease, making it more difficult to plan agricultural practices. They also think likely that extrem climatic conditions become more frequent, particularly in terms of intense rainfall, droughts and heat spells.
-=== Conclusions ===
-In the long run, the climatic change could affect agriculture in several ways :
-* ''productivity'', in terms of quantity and quality
-* ''agricultural practices'', through changes of water use (irrigation), agricultural inputs ([[herbicide]]s, [[insecticide]]s, [[fertilizer]]s)
-* ''environmental level'', in particular in relation of frequency and intensity of soil [[drainage]] (leading to nitrogen leaching), [[soil erosion]], reduction of [[biodiversity|crop diversity]]
-* ''rural space'', through the loss of previously cultivated lands, [[land speculation]], land renunciation, hydraulic amenities.
-They are large uncertainties to uncover, particularly the ''lack of information on the local scale'', 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.<br>
-If change is gradual, there will be enough time for [[biota]] adjustement. Rapid climate change, however, could harm agriculture in many countries, especially those that are already suffering from rather poor soil and climate conditions.<br>
-The adoption of efficient new techiques (varieties, planting date, irrigation...) is far from obvious. Some believe [[developed nation|developed nations]] are too well-adapted to nowadays climate. As for [[developing nation|developing nations]], there may be social or technical constraints that could prevent them from achieving [[sustainable agriculture|sustainable production]].
-== See also ==
-*[[Global warming]]
-*[[Global warming hypothesis]]
-*[[Global dimming]]
-==External links==
-* http://fr.news.yahoo.com/030512/202/36vt5.html
-[[Category:Climate change]]