Kudzu – a greenhouse gas producing weed

If you do not live in southern Japan, southeast China or the South Eastern States of the United States of America, you might not have heard of kudzu. Kudzu (pueraria lobata) sounds like a character Captain may ,meet but in fact is an oriental vine which has found (for it) a very satisfactory home in an area to the south and east of Texas to West Virginia. It is the classic weed- an unwanted plant in an unwanted place.

Kudzu has its uses; it is a legume so it replaces nitrogen in the soil and makes an excellent source of food for grazing animals. Its leaves are used to make drugs which may help in the treatment of migraine, cancers and allergies. Humans can eat its roots, which are rich in carbohydrate.

Kudzu was introduced into the USA just after the start of the Great Depression, as a means of combating soil erosion. The plant which grows very quickly and rampantly, found the climate of the South Eastern United States very much to its liking, where it is spreading at the rate of 150,000 acres a year, which is a greater surface area thanthe herbicides and mowing that is being used in an attempt to control kudzu can cover.

So far you might think kudzu is simply the old story of a plant, taken by people from where it is native, and planted in a new biosystem, running riot and dominating that new biosystem by pushing out native species. In England Japanese knotweed runs rampant in some places, causing damage to the roads, buildings and watercourses which it infests.

Kudzu has another string to its bow, so as to speak. It not only affects the soil and the biosystem dominating over other species, but it adversely affects the atmosphere. Kudzu increases nitric oxide emissions from soil as a consequence of increasing nitrogen in the soil. This in turn has the potential to increase ground level ozone, which provides those who live where kudzu infests with poor air quality.  I shall explain.

The process which means kudzu providing poor air quality is like that of many other legumes. Kudzu, through its root bacteria, transforms atmospheric nitrogen into ammonium (NH4). The NH4 oxidises transforming into that powerful greenhouse gas nitrous oxide. Ozone is also produced.

Ozone, is beneficial at very high altitudes where it filters dangerous light rays; however in the troposphere (the bottom three quarters of the atmosphere) ozone is a dangerous pollutant and a greenhouse gas. Burning of fossil fuel creates ozone, because nitrous oxide and carbon monoxide (emitted by the incomplete burning of fossil fuel) when exposed to sunlight produce ozone.

Some scientists worry that if we deplete the top (the “good”) layer of ozone from the atmosphere more UV radiation will penetrate the troposphere creating more ozone in the troposphere. This is still a theory, but the mathematics and chemistry of it works.

Recent studies show that where there is extensive kudzu invasion there are more than an extra seven high ozone days each year, making kudzu quite dangerous in terms of ozone production.

This low level ozone is dangerous; even very most increases in ozone (ten parts per billion increases over two days) seem to affect human mortality, as such increases are assoictaed with a 0.3% increase in the death rate. Higher ozone rates seem to create human respiratory problems and more asthma.

At NASA the scientists believe that ozone carried from the industrial lands to the poles is responsible for at least a third of the polar warming in winter and spring. The NSA Goddard Institute for Space Studies thinks that reducing ozone pollution is a good way to “ease” global warming in the polar regions.

Whether ozone is produced by burning fossil fuel or by the biological processes of kudzu, the ozone at low level is harmful to health of people and harmful to the planet’s overall health.

You can see the paper published on kudzu and ozone events at http://www.pnas.org/content/early/2010/05/12/0912279107.full.pdf

One Response

  1. I do not have absorption spectra for NO2 and would not expect it to be as effective in absorbing IR as water vapor, but the important point is quantity. Kudzo is such a small part of the biome the amount of NO2 produced by it has to be very small.

    NH4 is extremely soluble in water with 1100 volumes of it dissolving in a single volume of water, thus it is rarely observed in air.

    Kudzo has been a great pest in our southern states, but to add “greenhouse” gas to its’ crimes is a bit over the top. Water vapor is responsible for 99.9% of all atmospheric heating. CO2 is next in line with 0.01% and then methane with something like 0.0001% due to a poor absorption spectrum and an occurance of only 18 molecules per million.

    You can see several of these spectra at http://globalwarmingnotes.i8.com

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: