Great Lakes

Climate Changes

The continental United States experienced an extremely mild, warm 2011-12 winter season and while that may sound like a wonderful break from the snow and sleet for many people, it does have some apparent drawbacks. Many streams, rivers and lakes did not freeze this year and that has allowed plants and algae to grow unchecked. Additionally, insects which rely upon open water for breeding were able to breed longer in the fall and begin breeding earlier this spring.
In the Great Lakes, algae blooms can occur in the late summer when the lake waters have been warmed by the sun. In 2011, the algae blooms on Lake Erie were so large that they were visible from space and astronauts aboard the International Space Station sent pictures back to Earth. These algae blooms not only impact recreational use of the lakes by creating swimming restrictions, they also choke the water and starve it of oxygen, creating dead zones for fish.
Often, the Great Lakes are covered by ice and the spring waters are frigid; this year, however, large portions of the lakes were ice-free. As a result of this winter’s mild weather, the waters are warming more rapidly than the norm. Instead of blooms that are typically restricted to the months of August and September, 2012 may see blooms begin as early as May. The Great Lakes are a fragile, recovering ecosystem and it is not clear what the effect of widespread, persistent algae blooms would be on the waters or their inhabitants.
Additionally, the lack of ice cover meant increased evaporation this year. Ice is an excellent reflector of the Sun’s rays; deep, blue, dark water, on the other hand, readily absorbs the Sun’s energy and in turn fuels the evaporation process. Already, the Great Lakes water levels are down by 15-18cm for the year. The lower water levels also means shallower waters near shore which contribute to the algae blooms discussed earlier.
It’s not just water levels and algae that have folks concerned, however. The mild winter has allowed mosquito populations to breed early in much of the United States. In Missouri, for instance, mosquito season typically starts in late April and lasts into September. Officials in St. Louis County say they found active mosquito larvae in March this year. Workers are already in the field sampling standing water and storm drains to treat any breeding areas for mosquitoes. The St. Louis Department of Health predicts that this year will be a great year for mosquitoes – though not so great for the humans they feast upon.
Compounding that prediction is a new study published in the journal Biology Letters. The authors suggest that the mild winter we’ve just had may also speed up the transmission of disease from mosquito to human. The authors trapped one particular mosquito species for eight years, testing the DNA of the blood in the mosquitoes they trapped so it could be traced back to the source. In warmer years, the mosquitoes transitioned from biting birds to biting mammals in May or June, whereas in cooler years, the transition happened in August and September. The connection between mosquitoes, birds and humans is well understood when it comes to West Nile virus; the mosquito feasts on an infected bird and then passes the virus to a human when the mosquito feasts on their blood. That means that cases of West Nile may be on the rise in 2012.
While they may not be catastrophic, the consequences of weather anomalies are real and they may be a harbinger of things to come if the planet’s climate continues to change. Algae blooms will disrupt lake ecosystems and disease will impact lives. Finding ways to rapidly adapt to these situations and, more importantly, recover from them is critical to living in a changing world.