How do you make a spider angry?
There are all sorts of reasons to worry about global climate change: rising sea levels, greater risk of skin cancers, spontaneous combustion in San Antonio, etc.. Now we can add a new one to the list: according to an article in this month’s Nature magazine, spiders will soon be getting much, much angrier.
First, you add climate change
If you’re a climate change denier – or worse, an evolution denier – this story may not be much cause for concern. But for those living in the twenty-first century who prefer to believe in science, the combination of these two natural forces may soon bring us angrier, more aggressive spiders. While this isn’t quite as alarming as a Sharknado, or that time Spiderman turned really, really bad, it nevertheless offers some cause for concern.
Climate scientists are still debating whether rising global temperatures will have an effect on the frequency of tropical storms. This summer, for instance, the warmest on record, seems to be a quiet one for storm and hurricane activity. But the same scientists agree that a warmer earth will almost certainly mean greater frequency of the most intense weather events, from hurricanes to blizzards to ever more massive forest fires. Imagine more Katrinas; more droughts like the Millenium Drought, which struck south-east Australia in 2000 and lasted nearly 15 years; more heatwaves like the one in Europe in 2003 which killed more than 50,000 people.
Part of the reason such “black swan” weather events, as they are called, will gradually increase has to do with the rising temperature itself, which tends to destabilize weather patterns, such as the gulf stream, and create unpredictable events. Additionally, however, rising Ocean levels create warmer seas and warmer seas work to intensify storms. At the same time, these higher sea levels will result in much higher storm surges and increased damage, especially along coastal areas. So, while the number of hurricanes may decrease during a given season, extreme events will occur more and more often.
Next, you add evolution
The most immediate impact of these weather changes on spiders will likely be a reduction in their total population. If you’re an arachnophobe, or even just mildly uneasy around these creatures, that might sound like a positive outcome. But spiders play an important role in our global ecosystem. Among the many other valuable functions they serve, they prey on flies, earwigs, moths, roaches, and mosquitoes. In other words, a decrease in the spider population probably means an increase in all these insects and the problems they bring with them. As the Earth continues to warm, we should expect, for example, more cases of malaria, West Nile, and Zika.
But a decrease in spiders, a decrease that is already happening, can have other troubling effects as well. A recent study, which appears in this month’s issue of Nature, examines the impact of global climate change specifically on the Anelosimus studiosus species of arachnids. This species, like many other species of spiders, comes in two distinct flavors. One sort is relatively peaceful and relaxed, mild-mannered. The other is aggressive, more of a warrior. This type is useful because it protects the colony from attack. And the qualities that make it so tough also make it more likely to survive a catastrophic event such as a hurricane. Evolution means that the tougher the environment, the tougher the spiders.
Global climate change may be hurrying evolution along in this case. More catastrophes result in fewer peaceful spiders and more aggressive ones. And it turns out the aggressive gene is hereditary in spiders, meaning eventually there may be no peaceful Anelosimus studiosus left. Over the long term, angrier and angrier spiders. How angry? The warriors are far more likely to attack their own kind, cannibalize their own eggs and kill their own males.
Will this happen to other species?
Researchers studied only this one species, so it is unclear whether other species might be experiencing the same effects of climate change, or indeed if other kinds of animals might be going through similar evolutionary changes. Might we soon be facing angrier bears, angrier elephants, angrier birds? And most importantly, will there be enough angry spiders to fend off the angry mosquitoes?