Now that ample autumn rains have softened the soil, my main outdoor task is yanking Scotch broom seedlings — thousands of them. Each place I’ve lived has had its own particular alien invaders. The unholy trinity of privet, pistache, and Ailanthus (tree-of-hell) won the war at one home and took over the whole town. While I don’t expect to win the broom war, I hope to slow down colonization of my home territory and win the battle. . . eventually. Could be worse. The mosquitoes spreading Zika are invasive species. So are one of the largest snake species in the world, Burmese pythons. Due to global warming both might be moving into my territory, but President Obama is fighting on my side.
On December 6th, Obama increased national protection from non-human foreign invaders with an Executive Order: Safeguarding the Nation from the Impacts of Invasive Species. The Order notes that invasive species spread diseases and
...pose threats to prosperity, security, and quality of life. They have negative impacts on the environment and natural resources, agriculture and food production systems, water resources, human, animal, and plant health, infrastructure, the economy, energy, cultural resources, and military readiness. Every year, invasive species cost the United States billions of dollars in economic losses and other damages.
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The new Executive Order builds on one issued in 1999 and adds climate change to the mix.
Federal agencies shall consider the impacts of climate change when working on issues relevant to the prevention, eradication, and control of invasive species, including in research and monitoring efforts, and integrate invasive species into Federal climate change coordinating frameworks and initiatives.
climate change increases INVASIVE INFECTIOUS DISEASES AND their VECTORS
Climate change has already influenced the spread of infectious diseases and they are expected to become even more serious. Warming temperatures and flooding support some pathogens (e.g., cholera, giardia, salmonella) and mosquitoes that spread West Nile virus, malaria, dengue and yellow fevers, and Zika. Locally transmitted Zika infections occurred in Miami earlier this year and now are reported from Brownsville Texas. The mosquito that transmits Zika (Aedes aegypti) also can carry dengue and yellow fevers. Note that Brownsville is in the shaded area (current extent of the mosquito vector) on the map above, but the estimate of this mosquito’s abundance in July is low (yellow). Recent cases are from December and were caused by local mosquitoes. The weather in Brownsville has been warm and wet.
Disease vectors benefiting from climate change include more than mosquitoes. Ticks and the pathogens they spread have moved into areas where they once were uncommon. Hantavirus is carried by rodents like deer mice who survive and reproduce longer in the absence of cold winters. Flooding causes mice to come into homes seeking shelter and food, thus increasing our exposure to hanta.
INVASIVE broom IS THE bane OF my HOME TERRITORY
Directly outside the front door, my trouble is Scotch broom. I don’t have any large, flowering Scotch broom shrubs under the ponderosa pine trees in the forest patch that is my yard. But some must have grown around here in the past because carpets of Scotch broom seedlings emerged in response to the recent rainfall. Many are at the stage where one good yank uproots them and I know this means I need to be out there yanking. Once they grow more or the soil dries, it is difficult to remove plants without special tools and hard labor. Even forest fires don’t get rid of broom. Fires add more because the shrubs resprout from the roots and fire eliminates competing native vegetation while stimulating germination of dormant broom seeds in the soil. Scotch broom were introduced from Europe in the mid-1800’s and planted by homeowners as ornamentals and by the USDA for erosion control. They are still sold in nurseries but don’t let their pretty flowers trick you into buying them.
While Scotch broom blooms abundantly in early spring and provides lovely patterns of vivid yellow among green conifer forests, they are a nasty problem. The shrubs grow vigorously as both leaves and twigs are equally photosynthetic. They crowd out native plants, diminish habitat for grazing animals, and increase wildfire risk. Also, each shrub can produce 12,000 seeds a year that are released ballistically — shot out from the parent plant. Then rain, wind, wildlife and humans (e.g., mud on your shoes and tires) spread them even further. Some are ready to germinate as soon as water is added, while others can survive at least 80 years in the soil seed bank. That’s the brooms I’m fighting now — the soil seed bank’s contribution stored for years after the parent plants were removed. Some might be from seeds deposited into the soil long before I was born.
BUT IT COULD BE WORSE: WARNING SNAKES AHEAD!
Florida has invasive Burmese pythons, one of the largest snake species in the world. They can grow over 6 feet long in their first year after hatching, live for over 20 years, and average about 12 feet long (they can be nearly 19 feet long). Some were released by people who had them as pets and lost interest. In 1992 Hurricane Andrew demolished a breeding facility (and perhaps also zoos) that allowed pythons to escape. Did we need python breeding? Whose stupid (profiteering) idea was that? By 2007, Burmese pythons were established from southern to northern Florida.
With climate change warming northern states, the pythons might move into two-thirds of the continental U.S. along all three coastlines by the end of this century. They may be considered “docile pets” but they are also powerful and have killed humans. So yeah, let’s include climate change effects on invasive species because I don’t want to walk out my door and wade through pythons. Fortunately, this isn’t too likely because they need a permanent water source and my area has a long dry season. But young pythons also hang out in trees and I have lots of trees. Plus, we have rivers and pythons are good swimmers.
While 12 foot long pythons at my swimming hole sound awful, they haven’t arrived yet and are Florida’s problem so far. Deer mice spreading hantavirus are already here around my home, however, and potentially will be worse. Also, mosquitoes have been spreading West Nile virus locally for years and the Zika-carriers are closing in. These invaders make Scotch broom seem like a harmless pretty shrub, except I know that native habitat diversity minus broom is better for wildlife who help control mosquitoes (bats and frogs) and deer mice (fox, coyote, raptors, cougars). It’s better in every way.
Obama’s Executive Order requires several actions, including
- a National Invasive Species Assessment that evaluates impacts to food security, water resources, infrastructure, the environment, human, animal, and plant health, natural resources, cultural identity and resources, and military readiness [...] and
- advance national incident response, data collection, and rapid reporting capacities [for] early detection of and rapid response to invasive species….
Although I don’t think my invasive species — not even the Ailanthus whose root sprouts lifted the floor off my porch — affect military readiness, I’ll continue yanking out Scotch broom. Limiting its impacts to the environment, animal and plant health, and natural resources is part of my cultural identity.
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What invasive species is the bane of your home territory?