geography discussion 6
Cooper2021
Geograph110_24_drought2.pdf
Let’s learn further about the impact of climate change on agriculture. The US Global Change Research Program (http://www.globalchange.gov) is a very useful and informative site. In this lecture, some of the lecture slides refer to figures available from both the IPCC and US Global Change Research Program websites.
USGCRP 2015
In the US, the most valuable agricultural products are 1) Grains, 2) Cattle, 3) Poultry, and 4) Milk. With increasing climate change, we will see a greater impact to agriculture and associated industries, which consequently will have an impact on the US economy.
https://scied.ucar.edu/where-are-farms-united-states
Where are the farms in the United States?
Where are those farms found in the US? The darker green colored area shows a greater percentage of land use dedicated to agriculture.
Agricultural activity is distributed across the U.S. with market value and crop types varying by region. In 2010, the total market value was nearly $330 billion. Wide variability in climate, commodities, and practices across the U.S. will likely result in differing responses, both in terms of yield and management. (Figure source: USDA National Agricultural Statistics Service 2008).
Combined your knowledge about the main source for ground water in the west (e.g. Colorado River), and the high demand for ground water withdrawal for agriculture in that region. This figure shows where water stress exists in the US.
Let’s look at several specific agricultural products that are and will be affected by changing climate.
Projected Changes in Key Climate Variables Affecting Agricultural Productivity (2070-2099) compared to 1971-2000
Lengthening of the frost-free or growing season
Warmer-season crops, such as melons, would grow better in warmer areas, while other crops, such as cereals, would grow more quickly, meaning less time for the grain itself to mature, reducing productivity.
Reductions in the number of frost days (days with minimum temperatures below freezing)
Projected Changes in Key Climate Variables Affecting Agricultural Productivity
Increase of consecutive dry days (days with less than 0.01 inches of precipitation)
Increase in the number of hot nights
Negative impacts on crop and animal production 1. High nighttime temperatures affect plant metabolism and the
photosynthetic apparatus, particularly during reproductive stages, resulting in reduced grain yields (e.g. wheat).
2. Exposure to multiple hot nights increases the degree of stress imposed on animals resulting in reduced rates of meat, milk, and egg production.
This figure, also included in the IPCC assessment report, shows significant decreases in many agricultural products through this century. Please know that climate change will affect crops differently because individual species respond differently to warming temperatures in different seasons. Crop yield responses are projected under two emission scenarios: GHG emissions substanCally reduced (B1) and GHG emissions with conCnued growth (A2). The analysis assumes adequate water supplies and nutrients are maintained while temperatures increase.
Reduced Winter Chilling Projected for California
Grapes = 90 hrs Peaches = 225 hrs Apples = 400 hrs Cherries > 1000 hrs
Chilling hours = temperatures are between 32oF and 50oF over the winter
Area capable of producing grapes required for the highest-quality wines is projected to decline by more than 50% by late this century (Luedeling, E., M. Zhang, and E. H. Girvetz, 2009, PLoS ONE, 4)
Fig. 2.Winegrape cultivar diversity can impact the loss of current winegrowing regions (see SI Appendix, Fig. S14 for losses within all climatically suitable areas). Predictions of loss
are shown for scenarios of 2 �C warming (yellow bars) and 4 �C warming (red bars) relative to a 0 �C reference scenario. Shaded areas illustrate �1 SD around the mean loss for each number of cultivars, combining two
sources of uncertainty: 1) variability according
to all possible combinations of n cultivars (e.g., at one cultivar, that cultivar could be any of the
11 considered and each covers a different
area), and 2) modeled climatic suitability
under each climate change scenario (e.g., one
model member may predict suitability of an
area, while another does not). These results
are based on climatic suitability calculated
with all eight climate variables (Modeling Maturity).
(Morales-Castilla et al. 2020 PNAS,
https://www.pnas.org/content/117/6/2864)
A recent paper suggests that climate change could shrink optimal wine producing
regions dramatically.
Fain et al. (2017) Climate change and coffee: assessing vulnerability by modeling future climate suitability in the Caribbean island of Puerto Rico - Published before Hurricane
Maria (October 2017)
Coffee is a crop that needs warm days and cool nights, and has a specific set of growing conditions. Currently, only two percent of the land in the tropics that is appropriate for coffee growing is actually being cultivated. However, the forest area that is projected to be more suitable for growing is now at risk to make room for the expansion and industry’s rush to keep up with demand. That demand for coffee is expected to double in the next 30 years.
According to a study published by Climatic Change within 50 years coffee producing islands of the tropics could be incapable of growing one of the most highly demanded crops in the beverage marketplace. Not only are temperatures rising, but that also means the pests are rising, making growing conditions extremely difficult. It could lead to growers and companies going into new forest territory, causing more deforestation to grow a monoculture of coffee.
Where the Water Ends: Africa's Climate Conflicts
http://e360.yale.edu/feature/when_the_water_ends_a fricas_climate_conflicts/2331/#video
or
https://vimeo.com/103528480
This is the last topic related to future drought. I am specifically sharing this with you because it touches on the potential future possibility of a “climate war”. Although this documentary features a situation in Africa, it could happen in any part of the world when or where we have scarce access to water as a lifeline resource.
