More Sneezing and Growing Ahead
Longer growing season isn't all good news. You might want to buy stock in Claritin and Kleenex.
Growing Season is Getting Longer
In the late 1800s, the first freeze of the season in Des Moines would happen on average about October 13th. That average is from the first 30-year climatological span beginning in 1879. I will explain later why 30-year averages are used/preferred over long-term average.
With climate change, that average first freeze has been delayed until October 18th. In Waterloo, the delay is only by one day, but the trend is still the same. Many in agriculture celebrate a longer growing season, but there are downsides.
The Longer Growing Season: Why It Isn’t Necessarily Good News
As climate change reshapes our environment, one of its more visible effects is the extension of the growing season in many parts of the world. At first glance, this might appear to be a positive outcome. More time for crops to grow could lead to higher yields and increased food production, right? Unfortunately, the reality is much more complicated. While a longer growing season brings some benefits, it also introduces significant challenges that farmers, ecosystems, and food systems must grapple with.
Here’s why a longer growing season isn’t necessarily the good news it might seem to be.
Pests and Diseases Get a Boost
A longer growing season often comes with the downside of increased pest and disease pressure. As warmer temperatures extend into what were once cooler periods, pests like insects, fungi, and bacteria are able to thrive for longer. In regions where frost used to provide a natural control mechanism, many pests are now persisting year-round or arriving earlier in the season. This is already leading to more frequent infestations and outbreaks that damage crops and reduce yields . Farmers may find themselves forced to increase their use of pesticides, which has implications for both environmental and human health.
Pollinator Timing Mismatches
Crops depend heavily on pollinators, such as bees and butterflies, to reproduce. However, climate change is causing a mismatch between the life cycles of plants and their pollinators. Plants may bloom earlier than usual due to warmer temperatures, but if pollinators don’t adjust their schedules at the same rate, plants might not receive the pollination they need. Without proper pollination, crop yields can decline, even with an extended growing season .
Water Stress and Drought Conditions
A longer growing season typically means crops require more water. But as climate change intensifies, many regions are already facing water scarcity due to more frequent droughts and diminishing water supplies. Higher temperatures during the growing season lead to increased evaporation from soil and plants, compounding the demand for water. In areas where droughts are becoming the new normal, a longer growing season might actually put more strain on farmers trying to meet the water needs of their crops .
Soil Degradation Risks
With more days available to plant and harvest, some farmers may push their soil to the limit, growing multiple crops without allowing time for soil recovery. The traditional practice of leaving land fallow or rotating crops helps preserve soil structure and nutrients, but a longer growing season can encourage overuse. This would lead to quicker depletion of soil fertility and can increase erosion, making it harder to maintain healthy, productive farmland over time.
More Extreme Weather Events
Although a longer growing season sounds promising, it often brings with it a greater risk of extreme weather. Heatwaves, floods, droughts, and sudden storms are all becoming more frequent as the climate shifts, and these events can destroy crops just as easily as they extend their growth period . A farmer may benefit from a longer season but lose everything if a late-season storm wipes out the crop. The unpredictability of these extreme weather events makes farming more precarious.
Decline in Nutritional Quality
There’s another less obvious downside to a longer growing season—many staple crops, including wheat and rice, are becoming less nutritious as CO2 levels rise. Studies have shown that higher atmospheric CO2 concentrations can reduce the levels of essential nutrients like protein, zinc, and iron in crops . While a longer growing season might lead to more food being produced, that food could be less nutritious, undermining efforts to combat global hunger and malnutrition.
Shifting Crop Suitability
As temperatures rise, not all crops will benefit from the changes in growing season length. Some plants that thrive in cooler conditions might struggle in hotter climates. This means that farmers in certain regions might have to transition to new crop varieties or switch to entirely different crops, requiring significant investments in new seeds, farming techniques, and infrastructure . While this adaptation is possible, it can be expensive and disruptive, particularly for small-scale farmers.
Uneven Benefits Across Regions
It’s also important to recognize that the benefits of a longer growing season won’t be evenly distributed. Some regions might see a positive impact on agriculture, while others could face shorter seasons or diminished growing potential due to more erratic weather patterns. In some areas, longer seasons might help crops, but in others, extreme heat and drought could make farming untenable. This unevenness could lead to growing disparities in global food production, with vulnerable regions facing even greater food security challenges.
Longer Allergy Season
A longer growing season, driven by climate change, can significantly worsen seasonal allergies. As temperatures warm and winters become shorter, plants start growing and blooming earlier in the year, leading to longer periods of pollen production. This extended growing season means that allergens like pollen from trees, grasses, and weeds remain in the air for a more prolonged period, increasing the duration and intensity of allergy symptoms.
One of the major issues is that plants like ragweed, which are notorious for triggering allergic reactions, thrive in warmer conditions and produce more pollen over longer periods. In fact, studies have shown that higher levels of carbon dioxide in the atmosphere can increase pollen production, making allergy seasons not just longer but more severe. This extended exposure to allergens leads to prolonged periods of discomfort for allergy sufferers, who experience more intense symptoms like sneezing, itchy eyes, congestion, and even asthma attacks.
Additionally, the overlap between different pollination seasons is becoming more common. For instance, in areas where trees and grasses used to release pollen at different times, a longer growing season can cause these cycles to overlap, compounding the allergen load in the air. For people sensitive to multiple types of pollen, this overlap creates a more challenging allergy season, where relief is harder to find.
In short, a longer growing season amplifies the duration, concentration, and complexity of allergens in the air, making seasonal allergies more intense and widespread. It underscores one of the many subtle but significant health impacts of climate change that affect daily life for millions of people.
Why Meteorological Records Are Broken into 30-Year Increments
When studying climate and weather patterns, scientists often rely on data broken into 30-year increments, known as "climate normals." These 30-year periods are not arbitrary; they serve as a crucial tool for understanding the complex dynamics of our planet’s climate. But why exactly is this period favored over longer-term records that span centuries or even millennia?
The primary reason for using 30-year increments is the need for a stable and consistent baseline to analyze climate patterns. A 30-year period is long enough to smooth out short-term fluctuations and anomalies—such as particularly hot or cold years—that might distort the broader picture. This ensures that the averages derived from the data are statistically reliable, providing a solid foundation for understanding a region’s typical climate.
Another key advantage of the 30-year period is its ability to capture the natural variability inherent in climate systems. Climate encompasses a wide range of phenomena, including cycles like El Niño and La Niña, which can significantly influence weather patterns over several years. A 30-year span is sufficient to incorporate these variations, giving scientists a more accurate representation of long-term climate trends.
The 30-year period is also an international standard, established by the World Meteorological Organization (WMO). This consistency allows for comparison across different regions and time periods, making it easier to identify and analyze trends, such as global warming or shifts in precipitation patterns. The use of this standardized period enables scientists, policymakers, and industries to make informed decisions based on reliable, comparable data.
One of the key benefits of the 30-year increment is its balance between being long enough to show meaningful trends and short enough to remain relevant to current conditions. While climate change is a long-term phenomenon, shorter periods might not accurately reflect ongoing trends due to the noise of yearly variability. A 30-year span strikes a balance, capturing the essence of climate trends while still being recent enough to inform current analysis and decision-making.
This period is particularly valuable for comparison with historical norms. By breaking data into 30-year increments, scientists can compare the current climate normal with previous periods, helping to identify significant changes and assess the pace of climate change. For example, comparing the climate normals from 1961-1990 with 1991-2020 can reveal shifts in temperature, precipitation, and other key climate indicators.
But why use 30-year periods over longer-term records? The answer lies in the relevance of the data. While long-term climate records spanning centuries or millennia are invaluable for understanding deep historical trends, they may not be as practical for current decision-making. A 30-year period reflects the most recent climate conditions, incorporating the effects of recent climate change and making it a more accurate reflection of the conditions people and ecosystems are currently experiencing.
This relevance is crucial for decision-making in various sectors, including agriculture, infrastructure planning, and disaster preparedness. The data derived from a 30-year period is recent enough to be directly applicable to these decisions, ensuring that policies and plans are based on current, rather than outdated, climate conditions.
Moreover, the 30-year period strikes a balance between variability and stability. While a single year or decade might see significant anomalies, such as an unusually hot summer or a cold winter, a 30-year period is long enough to smooth out these short-term fluctuations. At the same time, it captures medium-term climate variability, such as multi-year droughts or wet periods, while remaining short enough to be relevant for ongoing climate monitoring and adaptation efforts.
Using 30-year increments also provides a consistent framework for analysis. This allows for standardized comparisons across different regions and timeframes, which is crucial for identifying trends, such as warming rates or shifts in precipitation patterns. Additionally, as climate conditions evolve, new 30-year normals are calculated, ensuring that the data remains current and reflective of ongoing changes.
In summary, while long-term climate records are essential for understanding the Earth's historical climate, the 30-year period is favored for its ability to provide a relevant, stable, and actionable framework for understanding and responding to the climate as it exists today and in the near future.
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