"And if the farmers have allowed just one field edge to go back to some kind of feral vegetation, where there's flowers, you look down, and there's a bee. They're always waiting around the edges for us to give them a chance to come back. We just have to give them that chance." Matt Forister
In the case of global agriculture and the effects on crop yields from our heating world, it is becoming clear that 2030 is the new 2100, a warning from multiple scientific researchers, including NASA. Excessive heat and changing rainfall patterns are the obvious worries for global food security. But, like the biosphere and the extraordinarily complex web of life, agriculture depends on that same web for pollinating food.
Recently a new study was published in Current Opinion in Insect Science. has found disturbing trends in heat threats to indirect threats to bees, crops, and their interactions are understudied.
Extreme heat threatens bees, crops, and their interactions and coexistence in physiology, phenology, and behavior which are critical interactions in food production. The study points out that crop flowers have lost nutritional value for pollinators. Mismatches between bee activity and when flowers emerge will increase with warming. To quote the study (behind a paywall) abstract — "Heat-stressed crop plants with reduced floral rewards may reduce bee foraging and nesting, limiting pollination services. Understanding how extreme heat affects bee–crop interactions will be essential for resilient production of pollinator-dependent crops in this era of climate change." Almost one-third of food crops are being disrupted because of excessive heat damage to the pollinator and the plants. Insects and the plant's ability to reproduce, develop and survive.
Most vegetable gardeners know the value of honeybees and bumblebees. But most of the world's roughly 20,000 bee species are solitary, and some, like the squash bee, feed exclusively on the flowers of squash and gourds. Squash bees, as their name implies, feed solely on pollen from squash and other gourds. In her compelling report on the study, Liza Gross found these solitary species larvae when provided "other types of pollen in the lab, they don't develop. Undernourished bees get smaller over generations, so they can't fly as far. And that means they'll pollinate fewer crops."
Lack of moisture in agricultural soils likely compounds the effects on food production, notably flowering.
Gross introduces the reader to Jenna Walters. Jenna is a "doctoral candidate at Michigan State University's Pollination Ecology Lab. She studied the temperate blueberry crop in Michigan during spring when blueberries flower in temperatures in the middle seventies. In 2018 however, springtime temperatures rose to a scorching 95 degrees. Waiting until after harvest, researchers were shocked that growers lost fifty percent of the berries, and the yield across Michigan was 30,000 pounds less than a typical year. Looking at other factors that could explain the loss, such as rain and wind, there was no further explanation but heat.
Excessive heat can interfere with photosynthesis and diminish the nutritional value of flowers, which in turn can impair the survival, development and reproductive success of pollinators that feed on them, including bees. It can also change the size of bees’ legs, wings and proboscis and even hinder their memory, all of which support efficient pollination.
“How extreme heat is affecting plant-insect interactions is super important,” said Matt Forister, an expert on plant-insect ecology at the University of Nevada who did not participate in the review. “Especially the timing of it.” It seems that extreme heat in late summer or early fall may be particularly devastating, Forister said. “In our last big look at butterflies across the West, we found that warming temperatures in the fall in particular predicted the worst butterfly season the following year,” Forister said, referring to his Science paper published last year analyzing decades of monitoring data from scores of locations in the West.
As for why fall heat seems to be driving the declines, he added, “We don’t really understand it.”
Excessive heat can also upset the synchronized pollination schedules critical to producing the almonds and citrus that earn California farmers billions every year. If bees and other pollinators reach peak abundance before or after crops flower, the altered timing will leave the insects without food and crops without pollinators.
This can be a particular risk for ground-nesting species like squash bees. Rising spring temperatures heat up the soil, telling bees it’s time to emerge from their nests. Warmer than normal temperatures may send bees out to forage before flowers emerge, Walters said. “And they’re going to starve for some amount of time.” Bees that survive will be malnourished and produce fewer eggs. Those eggs are likely to result in a higher ratio of males to females, because males require less pollen than females to develop. But it’s possible that pollen quantity and quality cause the male bias, Walters said. It’s a question she’s working on now.
Recent research has found that even a mild temperature increase can negatively affect seeds and fruits.
His study shows that mild heat does not affect plants in quite the same way as heat shock. “Plants react slightly less strongly when exposed to mild temperatures. The interesting thing is that this reaction to mild heat is not really necessary for the plant’s survival. You could say that the plant is ‘overreacting’; it’s anticipating a scenario with even hotter days to follow,” explains Jansma.
In tomato plants, longer periods of mild heat turned out to affect the production of plant hormones, the conversion of sugars, and the folding of proteins. All these changes combine to reduce pollen development, in turn leading to lower percentages of living pollen. “The plant no longer focuses on reproduction, but arms itself against external stress factors.”
Other researchers who did comparable research on rice plants observed that with every one-degree increase, flowers produced 10% less living pollen. “In principle, you don’t need that much pollen to fertilise a plant, but when the percentage of living pollen is low, the dead pollen block access to the pistil, thus preventing fertilisation.”
Yale Climate Connections wrote on CO2 — The familiar adage – too much of a good thing is a bad thing – applies to atmospheric carbon dioxide: In higher concentrations, it is a damaging pollutant.
But you may have heard a myth that nature’s balance doesn’t really matter. After all, CO2 is natural, and it helps plants and crops grow. That’s true. But it’s also misleading in that it’s only part of the story. A widely circulated myth suggests that adding extra CO2 to the atmosphere will fertilize plants and crops and make the world greener and better. Unfortunately, that turns out not to be true.
The myth that CO2 is plant food and that “extra” CO2 therefore can’t be bad is an example of a logical fallacy. It sort of sounds right, but it’s a major oversimplification. It’s appealing because it suggests that it’s okay to emit the pollution that causes climate change. But the myth is not true. It’s so oversimplified that it leaves out other important factors that help plants grow – and all of the damage that extra CO2 is causing. Just think of it in terms of “too much of a good thing is a bad thing” as, for example, with too much water causing a bathtub to overflow.
Nature is like a recipe, with each ingredient needed in just the right measure. A pinch of nutmeg gives pumpkin pie a rich, warm flavor, but a tablespoon of nutmeg would ruin the pie. A car’s engine runs on a precise blend of air, fuel, and spark. Overloading one element disrupts the whole system. Many aspects of nature operate in a similarly balanced way.
For example, the atmosphere has a specific recipe. CO2 and other greenhouse gases are an essential part of the recipe because they trap heat in the atmosphere. With no CO2 Planet Earth would be in a perpetual ice age. But a small amount of CO2 keeps the planet in the famous “Goldilocks and the Three Bears” condition: not too hot, not too cold, but the “just right” zone that’s ideal for life as we know it. Too much CO2 overheats the planet.
By studying Earth’s history, scientists have learned that when there was a lot of CO2 in the atmosphere, the planet was hot. In fact, the last time the Earth had as much CO2 in the atmosphere as it now does was the Pliocene Epoch, more than 3 million years ago. At that time, Earth’s atmosphere was 3.6 to 7.2 degrees Fahrenheit warmer (2 to 4 degrees Celsius) than it is today. And global sea level was 50 to 80 feet (15 to 25 meters) higher.
I could write forever on this topic and all the minute details of a healthy ecosystem. I hope this diary is educational enough that we consider saving the natural world rather than destroying it. Remember, honeybees and bumblebees are not always the most beneficial bees to save for crops. Wild bees may play a more significant role than we can imagine.
