Hothouse Earth: Plants and Climate Change
by Moses Seenarine, 12/19/17
Raising carbon dioxide levels are not necessarily good for agriculture. The benefits of CO2 for plants may be less than previously thought and potentially counteracted by the damaging effects of the proliferation of surface ozone. Agriculture has always faced the challenge of weather variability, and altered agricultural conditions under a transforming climate could exceed farmers’ ability to adapt.
Farming could easily become adversely affected by (i) extreme heat and escalating water demands; (ii) inflated frequency of severe weather events, such as drought and flood; (iii) sea level rise and flooding of coastal lands; and (iv) modification in crop nutrient content. Variability is also likely to occur in (v) the number and type of pathogens and pests affecting plants and livestock; (vi) altered use of pesticides; (vii) damage to fisheries and aquaculture; and (viii) mycotoxin contamination.
There are numerous fine-scale processes that can moderate vegetation responses to nitrogen deposits. While smaller amount of nitrogen may act as fertilizer, stimulating growth in plants, large accumulated amounts can (ix) decrease soil health and cause a loss in the number of plant species. These vital food security issues need to be dealt with and modeled into future plans for livestock expansion.
The reality is animal-based diets will become even less efficient and further wasteful as planetary heating intensifies. The FAO's 2006 and 2013 assessments do not fully factor in the effects of climate warming on plants and crops. In particular, as the land warms, drought may reduce tree productivity and survival across many forest ecosystems. If the vapor-pressure deficit continues to climb, forest drought-stress by the 2050s will exceed that of the most severe droughts in the past 1,000 years.
The world's food authority uses different baseline scenarios for improved land management for livestock over a 20-year period. But they model weather data from 1987 – 2006. This climate assumption is challenged by recent weather-related (a) lower crop yields, (b) feed crop failures, and (c) livestock die-offs. Upwards of 60% of crop yield variability can be attributed to climate irregularity. And unnervingly, this variation occurs in regions that are principal producers of major crops, like the Midwestern US, the North China Plains, western Europe and Japan.
Direct climate impacts to maize, soybean, wheat, and rice under a RCP 8.2 scenario could involve average losses of 400–2,600 calories, or 8 to 43% of the present-day total. Freshwater limitations in some heavily irrigated regions could necessitate reversion of 20–60 Mha (77k – 231k mi) of cropland from irrigated to rain-fed management, and a further loss of 600–2,900 Pcal.
These projections are a major cause for concern. Many subtropical arid and semi-arid regions will probably experience less precipitation. In wet tropical regions, extreme precipitation events will be further intense and frequent. Monsoon onset dates will start earlier while withdrawal rates are going to be delayed, resulting in a lengthening of the season. Tropical cyclones are expected to become extra intense, with stronger winds and heavier rainfall. In addition, variability of climate, such as El Niño events, has large impacts on crop production.
Africa will be the part of the world that is most vulnerable to climate variability and alteration. East Africa will experience further short rains, while west Africa will get heavier monsoons. Much higher temperatures could reduce the length of the growing period in some parts of Africa by up to 20%.
Excerpt from "Meat Climate Change: The 2nd Leading Cause of Global Warming," by Dr. Moses Seenarine.
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