Jonica, what a lively exchange! However, let us be brief lest we absorb much of the forum space.
If you really meant that the output of maize, rice and wheat has declined, then you are factually wrong. Of course, world cereal output fluctuates a bit from year to year, but on the whole the output of all three products you mentioned, as well as the output of cereals as a whole, have been increasing, not decreasing, over recent years and decades. I have already pointed you to the source (the only one with world coverage), i.e. FAOSTAT. Between 2000 and 2013, wheat output passed from 585.6 to 715.9 million tonnnes (Mt); rice (paddy) from 598.9 to 740.9 Mt; maize from 592.5 to 1018.1 Mt. For milled rice, deduct 35% from the amount of paddy. Cereals as a whole: 2060.2 to 2779.9 if rice is counted in its paddy state; if rice is counted in milled terms, all cereals output grew from 1860.7 to 2318.6 million tonnes in that recent period (2000-2013). In fact cereal output is at an all time high in 2013-14, continuing a steady rising trend since 1961 when the series starts.
If you meant that it was the rate of growth what "declined", i.e. that the growth of production decelerated, then you are also not quite right for cereals (the rate actually accelerated lately), and you are also wrong for total agricultural production (i.e. value of production at constant prices), because its growth did also accelerate in recent years compared with previous decades. Production increased, and growth rate accelerated, both for total production and for per capita production, at world level, for cereals and for total food and agricultural output. Moreover, all grew much more, and faster, in developing countries than in developed ones.
Concerning climate change, I agree (as the IPCC also agrees) that it may have both beneficial and deleterious effects, on agriculture and on other aspects. Regarding agriculture, projections of climate change lead to projections of future agricultural production in various parts of the globe, yielding different results in the various zones, some negative and some positive. On the whole, available projections suggest the net global effect would be negative, in this precise sense: the agricultural output of 2050 or 2080, with projected climate change, would be slightly lower than the same output would be in the absence of climate change. But the output in those future yeasrs would however be (with or without climate change) much higher than today, in both total and per capita terms, because of general factors determining agricultural growth, chiefly improvements in technology and productivity, and (to a lesser extent) a small increase in the use of land for crops.
Technology is advancing quite fast, and shows no sign of relenting. At the same time, the worldwide area of land suitable for crops would expand due to climate change (though it will shrink in some areas, and expand in others, with the net result of an expansion). This would be especially due to the vast expanses of land in the Northern Hemisphere that are constrained by cold, not by heat, and are expected to have a milder climate, enabling new lands for cultivation and giving a longer growing period to lands already cultivated, resulting consequently in more hectares and more potential production per hectare, if such hectares end up being cultivated (only some of them would). Elevated CO2 in the atmosphere would also help improve photosynthesis and plant growth, and (for C4 crops) reduce plant water needs. Also, global precipitation would increase, although not uniformly (some areas would become drier), and more rainfall is generally good for agriculture except perhaps in low floodable areas which may become unusable for crops if permanently flooded. On the whole those low floodable areas are smaller than dryland suitable for crops, so on the whole suitable land is expected to expand.
I have already cited studies documenting these claims. You have not cited any studies documenting your claim that wheat, maize and rice production have declined (or they growth rates decelerate, if that is what you meant). Do cite them, please.
Other aspects of your message are very interesting, but I'm only touching here on some aspects related to my previous comments.
@Jonica Otarra.
Jonica, what a lively exchange! However, let us be brief lest we absorb much of the forum space.
If you really meant that the output of maize, rice and wheat has declined, then you are factually wrong. Of course, world cereal output fluctuates a bit from year to year, but on the whole the output of all three products you mentioned, as well as the output of cereals as a whole, have been increasing, not decreasing, over recent years and decades. I have already pointed you to the source (the only one with world coverage), i.e. FAOSTAT. Between 2000 and 2013, wheat output passed from 585.6 to 715.9 million tonnnes (Mt); rice (paddy) from 598.9 to 740.9 Mt; maize from 592.5 to 1018.1 Mt. For milled rice, deduct 35% from the amount of paddy. Cereals as a whole: 2060.2 to 2779.9 if rice is counted in its paddy state; if rice is counted in milled terms, all cereals output grew from 1860.7 to 2318.6 million tonnes in that recent period (2000-2013). In fact cereal output is at an all time high in 2013-14, continuing a steady rising trend since 1961 when the series starts.
If you meant that it was the rate of growth what "declined", i.e. that the growth of production decelerated, then you are also not quite right for cereals (the rate actually accelerated lately), and you are also wrong for total agricultural production (i.e. value of production at constant prices), because its growth did also accelerate in recent years compared with previous decades. Production increased, and growth rate accelerated, both for total production and for per capita production, at world level, for cereals and for total food and agricultural output. Moreover, all grew much more, and faster, in developing countries than in developed ones.
Concerning climate change, I agree (as the IPCC also agrees) that it may have both beneficial and deleterious effects, on agriculture and on other aspects. Regarding agriculture, projections of climate change lead to projections of future agricultural production in various parts of the globe, yielding different results in the various zones, some negative and some positive. On the whole, available projections suggest the net global effect would be negative, in this precise sense: the agricultural output of 2050 or 2080, with projected climate change, would be slightly lower than the same output would be in the absence of climate change. But the output in those future yeasrs would however be (with or without climate change) much higher than today, in both total and per capita terms, because of general factors determining agricultural growth, chiefly improvements in technology and productivity, and (to a lesser extent) a small increase in the use of land for crops.
Technology is advancing quite fast, and shows no sign of relenting. At the same time, the worldwide area of land suitable for crops would expand due to climate change (though it will shrink in some areas, and expand in others, with the net result of an expansion). This would be especially due to the vast expanses of land in the Northern Hemisphere that are constrained by cold, not by heat, and are expected to have a milder climate, enabling new lands for cultivation and giving a longer growing period to lands already cultivated, resulting consequently in more hectares and more potential production per hectare, if such hectares end up being cultivated (only some of them would). Elevated CO2 in the atmosphere would also help improve photosynthesis and plant growth, and (for C4 crops) reduce plant water needs. Also, global precipitation would increase, although not uniformly (some areas would become drier), and more rainfall is generally good for agriculture except perhaps in low floodable areas which may become unusable for crops if permanently flooded. On the whole those low floodable areas are smaller than dryland suitable for crops, so on the whole suitable land is expected to expand.
I have already cited studies documenting these claims. You have not cited any studies documenting your claim that wheat, maize and rice production have declined (or they growth rates decelerate, if that is what you meant). Do cite them, please.
Other aspects of your message are very interesting, but I'm only touching here on some aspects related to my previous comments.