Tag Archives: invasive species

Bananas and Earthworms -Oh Boy

Invasive species come in all varieties, warm-blooded and cold-blooded animals, all kinds of plants, even fungi. Some are notable but cause little problems – armadillos, some are notable and troublesome – feral hogs, and some you never see but are dangerous – infectious bacteria and viruses in some biting insects.

Whenever a species is introduced to a non-native environment there can be negative consequences, earthworms for example. The last ice age covered North America as far south as southern Illinois. Any native earthworms would have been wiped out. After the glaciers receded, the upper midwest evolved for thousands of years without earthworms. Much later, that locale was populated with earthworms by incidental introduction from colonial ships from Europe. Rock and dirt used as ballast and dumped onshore was the likely method of introduction.

Generally speaking, worms are good as they churn and aerate the soil. But there is a dark side. Portions of hardwood forests in Minnesota and boreal forests in Canada have been negatively impacted by invasive earthworms. Fallen leaves accumulate on the forest floor and create a rich organic layer called duff. This duff layer is the natural growing environment for native woodland wildflowers. It also provides habitat for ground-dwelling animals and helps prevent soil erosion – basically natural mulch. When earthworms are present however they eat this leaf litter. In areas heavily infested by earthworms, soil erosion and leaching of nutrients may reduce the productivity of forest and even degrade fish habitat. Many tree seedlings, ferns, and wildflowers don’t survive this altered environment.

In the “unseeable” category of invasives are numerous fungi, smuts, rusts, mildew, mold, etc. Many of these are serious agricultural pests causing untold damage to food crops. The tropics where much fruit is grown for export are particularly susceptible. A new threat has recently come to the western hemisphere. Tropical plantations are subject to problems such as fungi because of the warm, moist climate and especially because plantations are generally monoculture. When only a single species of plant is grown in large concentration, the condition is likely to favor pests.

Guatemala alone exports over 3 billion pounds of bananas to the United States annually. All together we import over 8 billion pounds of bananas a year and this crop is at risk due to a fungus from southeast Asia. Although there are over a thousand varieties of bananas, 95 percent of all commercial bananas are essentially a clone of one – the Cavendish banana. It replaced a previous clone, Gros Michael or Big Mike. It succumbed to a fungus called fusarium wilt. A similar fate seems to await the Cavendish. In some parts of southeast Asia, a new variety of this wilt is reducing production there by forty percent per year. The wilt, a soil organism, just turned up in Colombia and could appear across central America.

Invasive species generally have an advantage as natural controls are absent. Monoculture acts to increase the distribution of the invader. Devastation of the banana crop in “northern triangle” of Central America will only serve to accelerate immigration to the United States as families seek some sort of income.

Dr. Bob Allen is Emeritus Professor of Chemistry at Arkansas Tech University.

Amphibian Pandemic

One of the unfortunate hallmarks of the human condition is our purposeful or incidental reduction of biodiversity everywhere we go. Most obvious was the elimination of large herbivores from woolly mammoths to giant ground sloths. This makes a certain sense as they were prey species which fed our rapid expansion across the planet.

Global warming, by forcing changes to the climate, impacts all life on the planet. Fauna are indirectly threatened by simple reduction of suitable habitat. The International Union for the Conservation of Nature (IUCN) has identified habitat loss as a main threat to 85% of all species described in the IUCN’s “Red List” (those species officially classified as “Threatened” and “Endangered”).

A common example is when forested areas are cleared and converted to agricultural use. The destruction of diverse forests in southeast Asia for use as palm oil plantations threatens everything from Orangutans to Tigers.

An incidental apocalypse is now occurring with amphibians worldwide. The class Amphibia has existed for over 300 million years. Today frogs, toads, salamanders, and the lesser known caecilians are dispersed worldwide and exist in a number in niches from rain forests to deserts. A northern most amphibian is the wood frog of Alaska which literally freezes up during the winter. When the weather warms it thaws and goes about its business.

Compounding threats to amphibians from habitat loss and climate change is a rapidly expanding pandemic of a Chytrid fungus, specifically Batrachorchytrium dendrobatidis (BD.) The fungus has been know for over a century in parts of east Asia and Africa but only in the past few decades has it spread worldwide.

There are several hypotheses for the mechanism of dispersion. In the 1930s a British researcher by the name of Lancelot Hogben, hence the eponymous Hogben test, found that injecting urine from a pregnant woman into the the African Clawed Frog induce the frog to lay eggs. The test was faster and didn’t require the sacrifice of the animal as was the case in the rabbit test. It was used on several continents from the 1940s to 1960s.

Recent study of the DNA of numerous samples suggests the origin of the BD dispersion began on the Korean peninsula in the early 1950’s. The Korean war, with the massive movement of men and materiel in and out of the area could have dispersed the fungus. The fungus can easily be transported on any kind of moist material, in addition to the amphibians themselves.

The global trade in amphibians for foods and pets is probably responsible for the dispersion of new strains which may be even more toxic. BD grows on the skin of amphibians. Amphibian skin is responsible for much metabolic activity such gas exchange. Essential electrolytes, Sodium and Potassium are also exchanged across the skin and it is a disruption of electrolyte balance that kills them.

Of the roughly 7000 amphibian species, 200 have recently been extirpated, and another 2000 are threatened. Nearly half of all amphibian species are in decline. Defenders of Wildlife here in the United States has called for the Fish and Wildlife service to ban the import of amphibians.

The moral of this story is that we ought to leave the critters be. Transporting them from hither to you could very well accelerate the amphibian pandemic.

atmospheric co2

Impermanent Permafrost

The planet passed a milestone by mid-May of 2013 – the atmosphere hit 400 PPM Carbon dioxide. The carbon comes from both natural and human caused sources. Decomposing plant matter releases carbon naturally whereas burning fossil fuels does so “unnaturally”. Plants remove carbon during the growing season, so there is a cyclic annual variation in total carbon in the atmosphere.

For hundreds of thousands of years there was a balance between winter releases and summer decreases. Beginning in the industrial revolution of the late 18th century, winter releases have exceeded summer decreases such that the average concentration has gone from about 280 to 400 PPM.

We have a new milestone this year. This year the winter release in the northern hemisphere reached 400 PPM, almost two months earlier than last year, March 12th to be exact. This is yet another measure of the accelerating pace of the change to the atmosphere.

Some who confuse weather with climate may claim that polar vortex indicates that global warming isn’t happening, but this is a weather phenomena that was peculiar to the eastern United States. California and much of the west coast saw exceptional drought and warmer than normal weather. The iconic Iditarod sled dog race from Anchorage to Nome was hampered this year by warm weather. Portions of the 1000 mile long course were free of snow and ice.

 2014 Iditarod

2014 Iditarod

Global climate computer models and recent observations show that the northern reaches of the planet are warming faster than areas closer to the equator. This can actually accelerate global warming due to certain feedback effects on the concentration of gases in the atmosphere.

The tundra is characterized as a treeless area where the subsurface soil remains frozen year round. During the brief summer the surface snow melts and grass and sedge grow. One might think that warmer weather and shorter periods of snow cover would be good for growth but in fact recent research suggest just the opposite. It appears that earlier snow melt and warming in the permafrost results in lower soil moisture and hence less photosynthetic productivity.

The warming in the arctic has other scary possibilities. Occasionally, reasonably well preserved but definitely dead whole animals have been recovered in the tundra. Scientists went searching for for smaller game and found a virus. The virus was found in tundra frozen for at least 30,000 years. The difference besides size is the fact the the virus was viable. The virus when thawed out was able to infect and kill amoeba.

giant virus

giant virus

The thawing of the tundra and its disruption by extractive industries stands a good chance of exposing animate life on this planet to disease vectors not seen for thousands of years or even never before seen. As just one example consider that smallpox, exterminated from the surface of the planet, could make a comeback. Some experts say that over the centuries it has killed more people than all other infectious diseases combined. The future is ours to protect or ruin.

Global Warming and Disease Vectors

Mount Nebo, along with other mountaintop resorts in Arkansas, began as a place for the well-heeled to escape the summer miasma in the Arkansas River Valley below. By the middle of the nineteenth century steam boats brought folks seeking respite from the mosquitoes which bred in the swamps and transmitted deadly diseases such as malaria and yellow fever. Public health measures have eliminated these diseases in the United States but climate change raises concern for their return.

Malaria endemic countries

Malaria endemic countries

Recently the Intergovernmental Panel on Climate Change released the findings of their fifth report:Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased. Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years.

A warming climate means a wider range for disease vectors such as mosquitoes, ticks and flies that carry viruses, bacteria, and protozoa. Examples of diseases born by these pests include malaria, yellow fever, dengue fever, and equine encephalitis to name a few.

current range of Chagas diease

current range of Chagas diease

Most worrisome is Malaria, a parasitic infection of red blood cells for which there is no real cure. Because of the complex life cycle of the parasite their has yet to be an effective vaccine developed. Malaria infects over two hundred million people world wide and kills about a million each year, mostly children.

The mosquito that carries yellow fever for which there is a vaccine also carries dengue fever for which there is no vaccine. The genus Aedes carries both these diseases, is endemic to northern Mexico, and as the climate warms is advancing northward.

These are some of the diseases we know about, but new diseases arise regularly. In the age of jet travel a new disease can move half the way around the world over night and a warmer climate can provide a more accommodating environment.

Every day as a result of burning fossil fuels for cheap energy the planet gets a little warmer, the weather a little more erratic and the oceans a little more acidic. Climate change has far-reaching consequences and touches on all life-support systems. It is a factor that should be placed high on a list of those things that affect human health and survival. The energy with the cheapest up front costs may be more expensive than imagined in the long run.

The Anthropocene

Scientists in general and particularly geologists measure time on our planet in epochs. For example the time from two and a half million years ago until twelve thousand years ago is called the Pleistocene. This time period was characterized by a series of long glacial periods. The current epoch is called the Holocene which began with the worldwide recession of the glaciers.

Recently some scientists have called for the naming of a new epoch called the Anthropocene, characterized by human influence on the planet due to our transformation of the atmosphere over the last two hundred years. Others contend that the start of the Anthropocene should be counted as starting much earlier. Modern humans have influenced the planet by churning the biosphere for close to a hundred thousand years. Our mobility has resulted in the movement, occasionally purposely, of many many plants and animals.

Wheat originated in Near East, corn in Central America, and rice in Far East. All are purposely cultivated world wide. The inadvertent introduction of some species has been the ruination of others. The inadvertent human dispersion of the black rat is a good example. It has caused the extinction of many bird, reptile, and other small vertebrate species across the planet.

The honey bee originated in Africa, and migrated to Europe. It was brought to North America by the colonists for honey production and has been a resounding success. Annually fourteen billion dollars worth of crops are dependent on honeybee pollinationhoneybee in the United States alone. Ironically the honeybee brought to North America by humans is now threatened by humans by the use of a class of insecticides known as neonicotionoids.

Non native earthworms were also brought to North America by the colonists but this time the importation was accidental. They came as part of the ballast of ships and in the soil of potted plants. Their introduction has been a mixed bag. Whereas home gardeners and those who fish extol the virtue of the earthworm, they are actually harmful to forests of northern North America.

Glaciers advanced to about the Missouri and Ohio Rivers and wiped out earthworms, if there were any to begin with. After the glacial recession, the forests returned and adapted in the absence of earthworms. The normal condition of the forest floor is a thick layer of slowly decomposing leaves. The presence of earthwormsearthworm accelerates this decay, removing an important organic layer that serves as seed beds for saplings, ferns, and wildflowers.

One of the newest accidental imports is another ant, called the Crazy AntCRAZY ANT for its erratic behavior and tendency to swarm. It first showed up in Houston TX and has been seen in southeast TX, southern Louisiana, southern Mississippi and and much of Florida. Where it occurs it either kills or drives out most other species of insects, spiders, small reptiles and birds. They will nest just about anywhere but are particularly fond of electrical wiring, causing a 150 million dollars a year damage in Texas alone.

We certainly live in a time of dramatic global human influence. We continue to change the composition of the atmosphere and hence the climate. We are making the oceans more acidic. We are dispersing uncountable numbers of species, generally with negative impact. And all these effects are causing extinctions of flora and fauna. My question for you is should we?