Bee’s and Climate Change

Bees are very important to the health of the planet. In fact, they are the most important group of pollinators for wild plants and farming. In the United States alone, honeybees pollinate 80% of the worlds crops. However, populations are declining (with about 10 million hives disappearing in just the last three years) because human development, pesticides, and climate change.

Since the early 2000s scientists have been sounding the alarm that pollinating bees are being stricken with disease or mysteriously vanishing from their hives.  Nearly two dozen species have disappeared from Britain since the middle of the 19th century, according to the study. While scientists aren’t clear on exactly what factors are behind bees’ decline, what is known is that climate change is also making life harder for bees.  There is a correlation between the agriculture industry and the decline of bees. Our increasing efficiency and dumbing down of landscapes (croplands, pastures, and meadows now grow only crops, no weeds or wildflowers) limit the resources on which these pollinators rely.

Loss of Habitat

Climate change is causing habitat loss as bees fail to migrate to cooler areas and establish new hives. A recent study on bumblebee migrations found that bee territories have shrunk by nearly 200 miles in North America and Europe.

Temperatures Rising

Furthermore, as average monthly temperatures rise, flowers bloom earlier in the spring, creating a potential mismatch in seasonal timing between when flowers produce pollen and when bees are ready to feed on that pollen. Even a small mismatch of three to six days could negatively affect bees’ health, making them less likely to reproduce and less resistant to predators and parasites.

Plants and bees have evolved together as they both benefit each other- bees provide a way for plants to reproduce by dispersing their pollen, and plants provide bees with nectar as a food source. Climate change is affecting pollination by disrupting the synchronized timing of flower blooming and the timing at which bees pollinate. Flowers are blooming earlier in the growing season due to rising temperatures, before many bees have a chance at pollinating the plants. Thus, when bees finally begin pollination there is limited nectar available and competition for these valuable resources becomes more intense. Due to climate change, there is a tendency for flowers to decline earlier on in the growing season than they had previously. This could affect bumblebees that require a pollen and nectar supply throughout the entire growing season to allow the queen to produce a colony. Therefore, bumblebee nesting activity and reproductive success are associated with the synced timing of flowering.

The concern is we don’t really know what environmental and genetic cues plants and pollinators use to manage this synchrony.  Some plant-pollinator pairs in a particular area likely respond to the same environmental cues, and it’s reasonable to expect they will react similarly to climate change. Other pairs use different cues, the pollinator emerging in response to air temperature, for example, while the plant flowers in response to snow melt.  What limits the growth is honeybees in the spring are those coldest of the cold nights, because what is happening in their colony is that they are in a cluster, and they have to keep the queen and the larvae at 93 degrees. They do that by eating lots of honey, and tensing their muscles, and generating heat. When it gets warm enough outside for them to maintain a temperature of 93 degrees, they start laying eggs around the edges of the cluster, and the cluster begins to expand. As long as the workers can keep the brood temperatures at 93 degrees, the eggs will grow into adult bees in about 3 weeks. But if a single cold, cold night in March intervenes, then eggs at the edges that the workers can’t keep warm will die. The cluster shrinks, and the colony must begin again. It is suggested that trees may not feel those cold temperatures in the same way because their roots are well insulated. The sun-warmed ground is slower to chill than the air, so trees may not be feeling the cold snaps in the same way that the bee colony does. Thus, flowering may occur before the bee colony has built up enough workers to take advantage of it, which means the hive will struggle to stockpile enough honey to sustain them through the next winter.

Disease

Honeybees are susceptible to parasites such as Varroa mites and the gut parasite Nosema ceranae, and environmental stresses may increase infections. Scientists first discovered the Nosema ceranae in the early 1990s in Asian honeybees. It has since spread to Europe and the U.S., causing shorter lifespans and colony collapse. A recent study found that lower temperatures were associated with lower prevalence of the parasite, indicating that higher temperatures as a result of climate change could result in more bees infected with Nosema ceranae.