As we enter the hottest documented summer in global history, extreme weather events pose a significant threat to already vulnerable regions. This year’s June was the hottest June on record, and Puerto Rico was no exception as the territory endured temperatures that felt as hot as 125 degrees Fahrenheit, according to the National Weather Service.
Extreme weather events have placed the islands as a cautionary tale on the rapid effects of climate change. Rising sea levels, longer droughts, and stronger, more frequent hurricanes are on the growing list of environmental concerns. However, the likelihood of extreme weather events occurring becomes more probable when we analyze the effects of global warming in the tropics.
Overall, extreme heat can have profound impacts on hydrological and geological processes that can greatly affect communities over time. In the case of Puerto Rico, the accumulation of heat over time means that the warming of the ocean will make for more intense tropical storms during hurricane season. These atmospheric phenomena will eventually go on to make drastic changes to the landscape.
According to Dr. Kenneth Stephen Hughes, Associate Professor in Tectonic Geology, Geochronology, Geochemistry, and Structural Geology at the University of Puerto Rico Mayagüez, long-term extreme heat has dire effects on the rate of erosion and can trigger landslides. Areas in the tropics with mountainous terrain, such as Puerto Rico, are particularly vulnerable to these natural hazards, as landslides can damage or destroy critical infrastructure such as roads, bridges, utilities, and buildings.
Hughes recalls how after Hurricane Maria hit the islands in 2017, extreme rainfall caused widespread landslides that became especially harmful to rural communities.
“[The] immediate emergency related to landsliding is often that communities become barricaded in,” said Hughes. “A lot of communities only have one small road that goes in and goes out. So if there’s a landslide on that road, people can’t get medical attention, supplies, food, and everyday items. Usually, when these things happen, we don’t have power as well.”
Often, landslides caused by extreme precipitation events (also encouraged by global heating) end up escalating into debris flows, very fast-moving landslides which can garner enough strength during a tropical storm to sweep a house away. Although landslides are a completely normal geological process, their potential for danger is often exacerbated by agricultural practices as well.
“Agricultural practices often […] make hillslopes more vulnerable to landslides,” Hughes explains. “Imagine that you’re going to plant a hillside full of citrus trees or banana trees or something like that. Well, taking out all of the native vegetation really reduces the root extensions and makes the soil much more available to move.”
If plans are not made to reduce the rate of landslides, there will continue to be a destruction of farmland, leading to crop loss and reduced food production. This can negatively impact food security and the livelihoods of communities dependent on agriculture. After Maria, it was estimated that the hurricane destroyed over 80 percent of Puerto Rico’s 2017 agricultural crop value, much of which was due to heavy flooding and landslides.
These weather conditions pose a threat not only to farmland sustainability but the future of the nation’s freshwater reservoirs as well. During extreme weathering events such as Hurricane Maria, over-sedimentation carries large amounts of soil and sediment downhill. When these landslides fill with rocks, mud, and debris enter rivers, bringing sediments either directly into the ocean or into reservoirs.
What worries researchers such as Hughes is that the amount of sediment in reservoirs affects a majority of Puerto Ricans who are dependent on these freshwater sources for potable water. Hughes has performed bathymetric surveys, where he and his team identified an excess of sediment in reservoirs after Hurricane Maria and found that some had about 15 years’ worth of sediment backup.
“These exceptional events take away our ability to store freshwater, and sometimes in Puerto Rico, we have the opposite of extreme rainfall, we have extreme drought,” said Hughes. “And so when we have a drought, our reservoirs don’t fill up as much.”
Something that has become an issue in recent years is flash droughts, which come and go very quickly due to the rapid onset or intensification of drought. These weather changes can quickly raise evapotranspiration rates and remove available water from the landscape.
According to Dr. Eric Harmsen, Professor in Agricultural and Biosystems Engineering at the University of Puerto Rico, “There are some lakes that are only partially full […] the one up in Guajataca lost about 30% of its capacity.”
“There are others that [initially] had much more storage capacity that have lost almost 80%,” said Harmsen. “And so [now] when we receive rainfall, a lot of the water just passes through.”
The consequences of these effects can be clearly seen over the last six years, according to the Washington Post-Kaiser Family Foundation survey that found that a year after Maria, 50% of Puerto Ricans reported their households could not get enough clean water to drink.
In the tropics, especially in the Caribbean, droughts, hurricanes, and heat are not uncommon. However, the ongoing trend of extreme weathering leads to the loss of essential biodiversity protectors.
In a territory already environmentally vulnerable, with millions of people exposed to hurricanes, droughts, and extreme heat events, the conditions are more than just uncomfortable. This is especially true for rural or impoverished communities that don’t always have access to proper air ventilation, cisterns, or hurricane-resistant infrastructure.
A common misconception about climate change is that its effects are always immediately catastrophic. The reality is much more sinister, often only noticeable to those already in the eye of the hurricane.
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