What pops into your head when you think of climate change? Probably images of devastating floods, raging wildfires, or parched earth. Coral bleaching or masses of refugees fleeing drought and famine may also make it to the list for the more climate savvy among us.
Not many would think of the vibrant wildflowers we see in parks, verges and highways as victims of climate change. Thousands of species of flowering plants, which populate our Garden Route and Cape Fynbos regions, may be at risk in the face of a warming planet, suggests a recent study published in the journal Frontiers in Plant Science.
The study conducted in the United Kingdom, a first-of-its-kind, found that Northern European wildflowers are likely to see a steep decline in abundance, with some areas forecast to see a decline of up to 40%.
Researchers made use of simulations, creating wetter and warmer conditions which are predicted to increase due to climate change. Under this new scenario, some species of plants produced flowers with 60% less nectar, and fewer or lighter seeds. Due to these changes, pollinating insects had to visit more flowers to gather the needed pollen and nectar, and visited each flower more frequently.
“Our results demonstrate that climate warming could have severe consequences for some species of wildflowers and their pollinators in agricultural systems, and shows that their community composition is likely to change in the future,” said lead author Ellen D. Moss, a research associate at Newcastle University in the UK
While theoretical studies have predicted that climate change could accelerate pollinator losses and wildflower declines, Moss’s study marks the first time scientists have put the theory to the test in an experimental setting. And previous climate change studies have focused on a small number of either plants or pollinating insects in a particular region, and not looked at the effects at a community level.
“This study adds to the weight of evidence that pollinators are at risk from multiple stressors,” said ecologist Jane Stout from Trinity College in Dublin, who was not involved in the study. “They are losing places to feed and breed, and they are stressed by pesticides, disease and changes in climate.”
Researchers sowed spring wheat and a few native wildflowers, which grow on wheat farms, in small agricultural plots in a North Yorkshire farm, as part of an experiment. They then heated some of these plots with infrared heaters to increase the soil temperature by 1.5°C and they increased the water supply by 40% to mimic the predicted wetter conditions for Northern Europe. The non-heated plots acted as a control to compare their results with.
For the 2014 and 2015 flowering seasons, researchers tracked the different plant species that grew in these plots, the number of flowers they produced, the volume of nectar in them, and the weight of the dried seeds resulting from the flowers. They also collected information about visiting insect pollinators, including their visiting patterns to both the experimental, and untouched plots.
The study reported 25 plant species and 80 insect species in 2014, and 19 plant and 69 insect species in 2015. Even with higher temperatures and increased precipitation, the types of plant species found in the plots did not change.
The study did report that wildlife abundance plunged by up to 40% in the heated plots with most of the plants in these plots also producing fewer seeds in the seed heads, and the seeds weighed much less than those in non-heated plots.
“A key finding is that not all wild plant species respond to experimental manipulation in the same way, and so the implications for plant communities, and their interactions with pollinators, are complex to predict,” Stout said. Nevertheless, the general decrease in both the abundance and the number of seeds produced is of concern, she added, “because loss of floral resources in the landscape is already a major driver of pollinator decline.”
The study also found marked changes in the feeding behaviour of pollinators in the heated plots. Hoverflies, honeybees and bumblebees, which were the most abundant insects, visited more flowers, and increased the frequency of their visits to the same flower to collect the nectar and pollen they needed.
“Fewer flowers and less nectar mean less food for pollinators,” Moss said, adding that such conditions may drive competition between pollinators and force them to choose less optimal flowers. “This could reduce their fitness and survival.”
According to the State of the World's Plants and Fungi 2020 report, globally, two in five plants, including wildflowers, are threatened with extinction due to land use change for agriculture, housing and construction. In California, which is experiencing increasingly hotter and drier winters due to climate change, studies have recorded a decline of wildflower species by 15% in 15 years. In the UK human activities have destroyed about 97% of wildflower meadows since the 1930s, with some plants on the brink of extinction.
The loss of wildflowers also has a knock-on effect on thousands of insect species, including pollinators like bees and herbivores like aphids, grasshoppers and caterpillars. It also hits populations of natural pest controllers like spiders, ladybirds and lacewings that take shelter in the meadows.
Studies show that, worldwide, a quarter of known bee species have not been seen since the 1990s, and loss of habitat is one of the primary reasons for the decline.
“Climate change risks crop pollination and our own food supply, but perhaps of more concern is the risk to wild plant pollination and our ecosystems and all the other benefits we get from them,” Stout said.
Tackling climate change by rapidly decreasing emissions would save at least some of the blooms, but in the meantime, there are other steps that could prevent a catastrophic future for wildflowers.
“The main things that will improve ecosystem resilience in the context of wildflowers and pollinators is to improve habitat quantity, quality and connectivity,” Moss said. “We need to leave more wild spaces for native plants and insects and try to connect these areas up so that these patches of high-quality habitat are not too small or too far apart.”
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