With the images of the September California wildfires slowly receding from the news cycle, the consequences of climate change have left the public eye for the time being. While the summer has left its mark on the Earth with scorched ground and suffocating heat waves, this coming winter could have its own devastating consequences. According to the NOAA, the temperature outlook for the northern continental United States is expected to be above normal. 45% of the contiguous United States is already in drought conditions, especially in the Southwest region. While winter temperatures have been steadily increasing since the early 1900s, winter of 2020-2021 is likely to be impacted by the variability of La Niña conditions.
While it may seem paradoxical, agriculture is heavily dependent on reliably cold winters. With the trend of consistently warmer winters, a butterfly effect of impacts has spread across the farmlands of the United States. Different crops have different temperature tolerances and seasonal lengths required for optimal growth. Orchard crops such as fruits and grapevines especially require longer periods of cold weather to adequately grow and produce fruit. Different fruits could require as many as 200-1000 “chilling hours,” or hours spent at temperatures between 32 degrees and 50 degrees Fahrenheit. Orchard crops need periods of cold weather to trigger a kind of hibernation to prevent new growth. If trees don’t get the proper amount of chill time, they will bloom out of season, making the trees more susceptible to disease and lower fruit yield. For instance, in California, it is projected that the amount of safe winter chill area will decrease by 50-75% by the mid-21st century, and 90-100% by the late 21st century. Georgia’s famous peach also suffered an 80% loss of crop yield in the winter of 2016-2017 due to inadequate chilling hours for the state’s peach trees. Similarly, the state of Michigan lost $200 million in cherry yields when a warmer winter season led to an earlier bloom of the state’s cherry trees.
The erratic winter temperature trends are having an impact on the ecosystem in addition to the agricultural sector. Pollinators and disease vectors alike are shifting their behaviors in response to milder winter seasons. The number of areas populated by bumblebees, one of the world’s most important pollinators for both crops and wildlife, has decreased by 46% across North America. As the growing seasons of plants have been impacted by warmer winters, so too have the behaviors of bee colonies. In the winter, bees cluster together in their hives to conserve warmth and live off of the honey they created in the spring to sustain themselves through the cold season. When the weather fluctuates during the winter season, bee colonies may mistake an abnormally warm day for the start of the spring season, leaving their hives to collect pollen and nectar. Unfortunately for the bees, plants have no pollen for them to collect in the winter, risking colony starvation as the bees consume more honey for energy to fly.
Bats also play an important role in agriculture, acting as pollinators, fertilizers, and pest control for our crops. With the warming of the winter season, bats in North America have started changing their migration patterns. Female Brazilian free-tailed bats have been migrating from Central America to Texas to breed 15 days earlier than they did 25 years ago due to the warmer weather. Endangered female Indiana bats are also experiencing disruptions in their reproductive habits as they hibernate in the winter while pregnant and then emerge in the Spring to hunt for insects. If pregnant Indiana bats awaken from hibernation too early and there are not enough insects in the winter, they could risk starvation, especially since they must eat more to support their pregnancy. The changing migration patterns of bats could threaten agriculture as the yields of many crops rely on the pollination and pest control provided by bats. If a bat colony arrives too early or too late to pollinate an area, it could be disastrous for crop yields.
As the climate has changed, farmers and scientists across the United States have had to adapt to protect their products. Farmers can try to adapt their planting seasons to the area’s yearly temperature trends or change the selection of crops to those that can withstand warmer temperatures. There is also the possibility of utilizing techniques such as agroforestry to mitigate the effects of climate change. Alternatively, crops genetically modified to be heat or drought-resistant could be useful in preventing plants from awakening from their chill phase too soon.
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