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OUT OF THIS WORLD | What's Up In Climate Change - a glance at the most important news about our warming world

Spiders are growing larger, but here’s why it’s a GOOD thing

Isabella O'Malley
Digital Writer/Climate Change Reporter

Wednesday, July 25, 2018, 11:47 AM - Arctic spiders are growing bigger, study finds relationship between climate change and suicide rates, conserving islands by rat removal, and the winter benefit of urban heat islands. It's What's Up in Climate Change.


Arachnophobes be warned - on top of rising sea levels, deadly heatwaves, and monstrous storms, a new study reports that wolf spiders are growing bigger thanks to warmer Arctic temperatures. While this observance might be unsettling for some, the good news is they are indirectly helping manage climate change in the North.

The Arctic is warming twice as fast as the rest of the planet largely due to rapid sea ice melt, and the physical changes in habitat alters how predators and prey interact with each other. Permafrost is particularly sensitive to warming, and when it decomposes and melts, microbes that thaw begin to convert carbon into carbon dioxide and further fuel the cycle of increased carbon dioxide and warming.

Thawing of permafrost caused the road to drop, Alaska. Credit: Wikimedia Commons

To investigate how climate change can affect entire ecosystems, the researchers analyzed plots of land in Alaska and found that Arctic wolf spiders are thriving with earlier snowmelt in spring months, and that they are becoming larger and producing more offspring.

In their trials, they found that increasing the number of wolf spiders on a plot reduced the densities of their preferred prey, springtails, and increased the decomposition of permafrost. However, when temperature warming was adding to the trial, the spider densities did not have measurable effects on springtails or any other prey, who ate more microbes and fungus, which slowed the rate of permafrost decomposition.

The contributors to this study state that because the Arctic is warming at such a rapid pace, wolf spider densities could become even higher in the future, which might help manage permafrost melt and the microbial release of carbon dioxide. Researchers are continuously trying to understand the confusing, interconnected relationships between the Earth's surface and temperature rise, and this study demonstrates that extremely small changes in one species can have cascading effects to the rest of the environment.


There is an increasing amount of research into the connection between mental health and the environment, and a new study reports that there is a relationship between abnormally high temperatures and suicide rates.

Credit: Wikimedia Commons

Suicide rates in both the U.S. and Mexico are on the rise and the experts say contributing factors include economic downturns, unemployment rates, substance abuse, reports of celebrity suicides, and limited access to mental health care. Experts could soon include environmental factors as the study finds that suicide rates increased 0.68 per cent in the U.S. between 1968-2004, and 2.1 per cent in Mexico between 1990-2010 when there was a +1 degree Celsius increase in monthly average temperature.

In addition to analyzing historical temperature data and suicide reports, over 600 million tweets from Twitter were evaluated to see if abnormally warm monthly temperatures elevated the expressions of depressive feelings on social media. Previous studies have shown that Twitter has been used to predict variation in suicide in the U.S., and this study found that each additional +1 degree Celsius in monthly average temperature increases the likelihood that a tweet is depressive between 0.36 and 0.79 per cent.

Overall, the analyses conclude that by 2050 warming temperatures could increase suicide rates in the U.S. by 1.4 per cent and by 2.3 per cent in Mexico. However, the researchers note that there are strategies and programs that could significantly offset the increased risk from climate change - national suicide prevention programmes in OECD countries could reduce suicide rates by over 7 per cent and gun restriction laws in the U.S. could reduce the suicide rate by 5 per cent.

The study states that rising temperatures and climate change are not the direct motivators of suicide, but can increase risk by affecting the likelihood that an individual situation could lead to self-harm. The findings show that if carbon emissions continue on a 'business as usual' pathway, there could be between 9,000 to 40,000 additional suicides in the U.S. and Mexico by 2050, which could prompt a public health crisis in addition to the ongoing health challenges already being caused by climate change.


The lush, tropical vegetation of the Palmyra Atoll, an island territory belonging to the United States, had been ruled by rats until recent intervention by scientists.

Aerial view of Palmyra atoll. Credit: Wikimedia Commons

Palmyra atoll is located in the middle of the Pacific Ocean and is 1,600 kilometres southwest of the Hawaiian Islands - it's remoteness created incredibly unique biodiversity that is sensitive to the non-native rats that easily took over since there were no existing predators and abundant sources of food. The rodents quickly infiltrated all corners of the atoll and consumed such high amounts of tree seedlings that vegetation began to suffer and tree cover shrank.

During the past hundred years the atoll has been visited by sailors and government ships, and stowaway rats were likely the source of their unintentional introduction to the atoll. Non-native rodents have invaded approximately 80 per cent of all island groups on the planet and pose a serious threat to native biodiversity.

To improve the success of native species and restore the atoll’s natural habitat, rats were eradicated in 2011 and researchers studied how the atoll's vegetation changed over five years. Tree seedlings were able to grow in the soil without being eaten by the rodents and the researchers found that the number of seedlings for four out of five native tree species increased by more than 50 times - before the study there were less than 150 seedlings and after there were over 7700.

Land use change, pollution, and other human activities are causing a loss of species that is estimated by scientists to be between 1,000 and 10,000 times higher than the natural extinction rate. The success of reviving forests and vegetation on Palmyra atoll shows that species management is a promising tool for restoring rare environments.


July has had record-breaking heat waves around the world, and the millions living in cities filled with concrete and asphalt had an addition 1 to 3 degrees Celsius to deal with. Just a few degrees difference can result in serious health consequences and cause the city's energy-demand to soar, but new research shows that this dynamic could offer some benefits in the cooler months of the year.

The urban heat island (UHI) effect occurs because a city's constructed environment absorbs heat, produces more heat from cars and appliances, and has limited vegetation and plant cover - all of which contribute to health problems during times of higher temperatures. However, scientists from Princeton University conducted a study that found the UHI effect could benefit cities during the winter months by shielding them from extremely cold temperatures.

The Urban Heat Island effect is caused by lack of vegetation in cities and infrastructure made out of materials that trap heat. Credit: Wikimedia Commons

Their study finds that in cold temperatures heat islands had reduced heating demands in buildings, which significantly impacted annual energy consumption. The average number of days that require heating are more than three to 15 times more frequent than days needing cooling in North American cities like Chicago and Boston, and reversing the UHI effect would increase heating energy demands and associated carbon emissions.

The researchers note that initiatives to help cool cities during high temperatures, such as green roofs, would remove the UHI effect during cold temperatures, and that a paradigm shift is urgently needed so cities can consider the annual sustainability impacts, instead of just focusing on the warmer months. A solution that the study offers to balance the UHI benefits in all months is to incorporate colour-changing building materials that will adjust based on the temperature and whether heat should be reflected or absorbed.

Sources: PNAS | Nature - Climate Change | PloS one | Journal of Applied Meteorology and Climatology


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