Living with Invasive Species

What should be done when non-native species introduced into an ecosystem begin to outcompete native species? Should such invasive species, as they are called, be eradicated before they do serious damage to an ecosystem and lead to a loss of biodiversity? The traditional answer is yes, according to many conservationists. But the sad fact is that that most invasive species eradication efforts haven’t been very effective.

More recently, some conservationists are beginning to rethink the problem of invasive species. Perhaps invasive species should be viewed as a more normal part of the constant change that has been shaping our world since life began. Containment rather than eradication seems to be the new buzzword. Ecologists who study the effect of invasive species on ecosystems say that over time, native species begin to compete more effectively against invasive species. It may take decades or even centuries, but eventually a new ecosystem balance is likely to be achieved, with or without human intervention.

Transgenic Chickens Resist Bird Flu

By inserting a small piece of DNA into chickens that interferes with bird flu viral replication, scientists have developed transgenic chickens that are genetically resistant to infection by the bird flu virus. The inserted DNA fragment blocks a key enzyme required by the bird flu virus for replication of its RNA. Transgenic chickens exposed directly to the deadly H5N1 bird flu virus still get the flu and die, but they don’t pass it on to other birds in the flock. From an economic point of view, losing a few chickens is a lot less damaging than having to destroy a whole flock to try to prevent the spread of the disease. Flu-resistant transgenic chickens might also reduce the risk of a bird flu pandemic among humans some day.

Flocks of transgenic flu-resistant chickens could be widely available within a couple of years. That’s IF regulators decide that they and their eggs are safe to eat, and IF the public accepts them. Both are big “IF”s.

China's Future Water Shortage

China is depleting its underground water reserves in an effort to increase its agricultural productivity, according to a news article in Science magazine. Hundreds of thousands of wells were drilled in the North China Plain over the past 40 years, turning the plain into a fertile corn- and wheat-farming region. But the water table in the North China Plain is now falling at an alarming rate. Many of the wells are expected to run dry within the next couple of decades, putting at risk China’s ability to feed its growing population.

Water in deep underground aquifers exchanges only slowly with surface water. According to experts, some of the water now being drawn out in the North China Plain aquifer has been underground for 30,000 years. It might be that long again before it could be replaced naturally. In other words, water in deep underground aquifers should be thought of as a non-renewable resource, like coal, oil, and gas.

The U.S. Birth Rate is on the Rise

A record 4.3 million babies were born in the U.S. in 2007, according to a summary of birth statistics published each year in the journal Pediatrics. The birth rate (number of births per 1,000 women) has been climbing for a couple of decades, though it is nowhere near what it was 100 years ago. The record high number of births is due both to a recent trend upward in the birth rate and the larger U.S. population now than 100 years ago.

A noteworthy trend in the data is that women are having their babies later than they did just 15-20 years ago. Birth rates were lower in 2007 than in 1990 for women under 30, but higher in 2007 for women over 30. Also noteworthy is a continued rise in the number of births to unmarried women; it’s now a record 40% of all births.

Feeding the World in 2050

Forty years from now will there be enough food to supply the world’s growing human population? Perhaps the best answer is “It depends”. It depends on how much we can improve the energy efficiency of producing and transporting food. It depends on what we are willing to eat (“Excuse me sir – would you like the beef or the crickets?”). It depends on what we do about climate change, how much damage we do to the environment, and how efficiently we use our precious supplies of fresh water. It depends on whether we’re willing to use genetically modified crops.

A special section of Science magazine available online examines some of these and other issues on the subject of food security. There are some pretty interesting and thought-provoking ideas out there. There’s even an article on what kinds of careers might be available for persons interested in this subject.

Carbon Dioxide and Forest Growth

Plants require carbon dioxide (CO2) for growth. How are they affected by the rise in atmospheric CO2 that occurred over the last century, as a result of human activities such as the burning of fossil fuels? Do plants use more CO2 (i.e, grow faster) when more CO2 is available?

There is some evidence that they may. A study of 55 forest plots in the Eastern United States reveals that the tree biomass is increasing at a faster rate now than in several decades past. After factoring out other known factors, the most likely causes appear to be increases in atmospheric CO2 and in temperature. This may be good news, for it means that as the atmospheric CO2 rises, some of the excess CO2 may naturally be stored in Earth's forest biomass. This could be slowing the rate of rise of CO2 (and global warming) that would otherwise occur.

Phosphate Recovery From Sewage

In this blog (June 1, 2009) I talked about the world’s dwindling phosphate supplies, and how the key to sustainability of phosphate supplies would be recycling. But who among us has even thought about how we might recycle the gram and a half of precious phosphate we excrete in urine every day?

Well, a researcher at the University of British Columbia did, and then he set out to do something about it. Today, a phosphate recovery system based on his design is producing about a ton of slow-release phosphate fertilizer every day from a sewage treatment facility serving Portland, Oregon. The fertilizer is in such high demand that the recovery system will pay for itself in less than five years. Other recovery plants are planned, including larger ones to recover the waste from dairy and pig farms.

So if you live in Portland, Oregon, count yourself lucky; you already ARE recycling your phosphate! (Or at least somebody is.)

Reference: Tweed, Katherine. Sewage’s Cash Crop. Scientific American Nov. 2009, p. 28.

Measuring Groundwater Depletion

Scientists are using satellite data to measure changes in the amount of water in underground aquifers. How do they do it? Satellite speed is affected by the pull of gravity, which is partly determined by how much water is underground near Earth's surface. As the first of two satellites approaches a region of the Earth with a large underground aquifer, the pull of gravity increases and the satellite speeds up briefly, increasing the distance between it and a trailing satellite. As the second satellite passes over it too speeds up briefly, closing the gap again. By measuring the changes in distance between the two satellites as they pass over the aquifer and then comparing those distances from year to year, scientists can determine changes in the pull of gravity over time and then estimate how much water has been gained or lost.

Using this technology, scientists have discovered that in just six years, one of the largest aquifers in India has lost a volume of water equal to a lake 30 feet deep and nearly 5,000 square miles in surface area. Most of the groundwater consumed in the region is used for agriculture. Nobody knows how large the aquifer really is or how long it would take to deplete it, but losses of this size just are not sustainable in the long run.

We can expect more of this kind of useful information as the satellite technique becomes more sophisticated. But will we choose to change our water use practices as a result of what we learn?

Wildfires, Evolution, and Ecosystems

Fires set by the forces of nature have existed on the Earth since the dawn of time, and as a result some plants have evolved to survive fires rather well. A few plants even require an occasional fire in order to release their seeds. But here’s an interesting notion; did certain plants evolve to encourage the spread of wildfires once they’ve started? After all, if the plant could survive the fire it might be a good way to kill off the competition. For those of you interested in evolutionary processes, see the recent well-referenced opinion article in the New York Times.

Swine Flu Takes Hold in Argentina

Swine flu just won’t go away. A recent a sharp uptick in the number of deaths from swine flu in Argentina has moved that country into third place for the most swine flu deaths, after Mexico and the United states. And the timing couldn’t be worse; it’s winter in South America, the season when influenza viruses typically spread the easiest. Of special concern is that the death rate in Argentina (1.6%) is more than three times the world average.

We need to keep an eye on this pesky bug. Who knows what it could do in North America NEXT flu season? For the latest information on swine flu (also now called Pandemic H1N1), see the World Health Organization website.

The Pandemic of 2009

The World Health Organization has officially declared a pandemic as a result of the rapid worldwide spread of Influenza A (H1N1), formerly known as swine flu. But that does NOT mean that a lot of people will die. By definition, a pandemic is simply a widespread outbreak of a new human flu virus that spreads rapidly from human to human, causing human illness.

Some flu pandemics cause only mild symptoms and few deaths – others can be quite deadly. The best-known pandemics of the last century were the deadly Spanish flu of 1918 (20-40 million deaths), and the milder Asian flu of 1957 (1-4 million deaths) and Hong Kong flu of 1968 (also 1-4 million deaths). In contrast, the milder seasonal flu that many of us get nearly every year kills “only” about a quarter of a million people each year.

Pandemics are of concern to public health officials (and the public!) because the virus spreads so quickly and because the consequences of the spread cannot always be predicted in advance. Fortunately, it now appears that this pandemic will be no more deadly than the typical seasonal flu that many of us get nearly every year. Most people who become infected with Influenza A (H1N1) are recovering without the need for medical care. But it could have been otherwise, and that’s why health officials were so concerned at first and why they are still watching it closely.

The other flu we worry about is avian flu (see Human Biology 5th ed., pp. 540-541). Avian flu is VERY deadly in the few cases in which it has been caught from birds, but human-to-human transmission is still exceedingly rare.

Dwindling Phosphorus Supplies

The world’s supply of phosphorus for agricultural fertilizers is dwindling, according to a recent article in Scientific American. Global reserves are expected to run out in about 100 years unless new reserves are found or better techniques are developed for extracting phosphate from phosphate-rich rock.

As phosphorus supplies decline and as the world demand for agricultural fertilizers grows, we can expect fertilizer price spikes, phosphate shortages, and perhaps even disruption of food production. Countries with large phosphorus reserves such as Morocco will benefit economically. Morocco could be among the wealthiest nations in the world in 50-100 years.

Food Shortages and World Stability

Will the world ever simply run out of food? A recent article in Scientific American suggests that it won’t be that simple. The article’s author postulates that local or regional food shortages will be followed by starvation, which in turn could result in the collapse of governments and a rise in terrorism in poor countries and refugee problems in neighboring countries. Countries most likely to become the first failed states include Somalia, Sudan, Zimbabwe, and Chad, according to several international peace groups. Destabilization of governments could eventually spread worldwide, if food prices rose beyond the means of less wealthy nations.

Could such a scenario be prevented? The article goes on to say that in the long run, maintaining the world’s food supply will require drastic action, including solving the global warming problem, conserving fresh water, and stopping the current rate of topsoil losses. Otherwise, we may all be fighting each other for the last scraps of food sooner (perhaps in just hundreds or thousands of years) than we think. It’s something to think about.

Reference: “Could Food Shortages Bring Down Civilization?” Scientific American pp. 50-57, May, 2009.

If Not Bird Flu, Then.....What?

In Human Biology 5th ed. (pp. 540-541) we discuss the possibility that a human pandemic might be caused by the bird flu virus, H5N1, if the virus evolves to become easily transmissible between humans. But so far it hasn’t happened. Where will the next great human pandemic come from, if not from the bird flu virus? No one knows for sure, but the smart money is on pathogens living in animal species closely related to humans, such as non-human primates. In fact, that’s precisely how HIV developed – an evolving virus in monkeys jumped to chimpanzees and then to humans.

Knowing this, how might we prevent the next pandemic, or at least have some warning that it was coming? One intriguing possibility would be to keep a close eye on diseases that develop in humans who are in close contact with wild animals. To learn more, read “Preventing the Next Pandemic”, by Nathan Wolfe (Scientific American, April, 2009, pp. 76-81), and then check out the website of the Global Viral Forecasting Initiative. In fact you can download a .pdf file of the Scientific American article directly from the the GVFI website.

Limits to the Human Population

In Human Biology: Concepts and Current Issues, 5th ed. we describe the theoretical limits on any population’s growth (Figure 23.2) and show the growth of the human population since the dawn of human history (Figure 23.3). How close is the current human population of 6.8 billion to Earth’s human carrying capacity? According to Jeffrey Sachs, Director of the Earth Institute at Columbia University, “We still do not really know”.

See “The Specter of Malthus Returns”. Scientific American September 2008, p. 38. Your students could read and appreciate Dr. Sachs’ one-page opinion piece on the subject. In my class the article led to a spirited discussion of the wide disparities in resource utilization by different countries.