RESPONSE OF PLANT SPECIES TO CO2 LEVELS
By Dennis T. Avery
Will the extra CO2 affect the biodiversity of the earth? Some have claimed that C3 plants (e.g., wheat) will now out-compete C4 plants (e.g., corn), that weeds will outgrow crop plants, and tall forest trees will shade out the understory species. (The C3 and C4 plants have different patterns of photosynthesis.)
However, Craig Idso, of the Center for CO2 Science, says we shouldn’t expect much change in our plant diversity due to the expected higher CO2 levels. Idso, trained in agronomy and geography, sees no clear threat to the earth’s species richness.
As an example, he notes, C3 plants like wheat have shown a larger growth response to higher CO2 levels than C4 plants. C4 plants like corn, however, appear to gain more in their ability to raise their water use efficiency — perhaps because they seem to make better use of the mycorrhizal fungi around their roots. The two sets of advantages seem to cancel each other out. Nitrogen-fixing plants seemed to have an advantage over non-nitrogen-fixers — but that was in studies inside greenhouses. Outdoors that advantage disappeared.
One study found that weedy mustard was strongly stimulated by more CO2 in the atmosphere — but no more so than most of the crop plants. On the other hand, says Idso, one of the major British weedy bracken plants seemed to get no stimulus at all from higher CO2 levels — which could put this weed at a disadvantage in the higher-CO2 future.
In the forests, says Idso, there seems little likelihood that the taller trees will shade out the understory species. Kerstiens reviewed 15 tree studies, and found that the shade-tolerant trees were twice or three times more responsive to added CO2 than the sun-loving tall trees. So, even if far less sunlight got through the CO2-stimulated upper tree canopy, the understory plants would still be vigorous and competitive. On grassland near Basal, Switzerland, elevated CO2 marginally increased the species diversity.
Hodge found that the increased CO2 levels also induced an increase in soil organic matter, and this seemed to stimulate beneficial soil fungi. Van der Heijden demonstrated that increasing the number of soil fungi species increased ecosystem plant diversity substantially.
None of this reassurance about plant diversity in a world with higher CO2 concentrations should come as startling news, says Idso. After all, most of our plant species evolved originally in much higher atmospheric concentrations of CO2 — up to ten times as high.
In terms of temperatures, every species still extant has persisted through 10,000 years of the Eemian Warming before our last Ice Age, which was about 5 degrees Celsius warmer than today, according to the University of Copenhagen. Each of our species then lived through the Ice Age itself, with a probable drop of 6-10 degrees Celsius that lasted for 90,000 years! That’s a range of about 11-16 degrees Celsius just in their “recent” experience. Where did we get the idea that these tough, competitive organisms were fragile?
You could say that the plants now are “just getting back to their roots.” The real lesson of this survey of plant responses to changing CO2 concentrations is the resilience of our wild species. Worry about humans in a full blown ice age, not plants happily absorbing CO2.
2. C3 and C4 plants — biology on line; www.biology-online..org/biology-forum/about 459.
3. B. Hodge et al, 1998, “Characterization and microbial utilization of exudate material from the rhizosphere of Lolium perenne grown under CO2 enrichment,” Soil Biology and Chemistry 30:1033–1043.
4. G. Kersteins, 1998, “Shade-tolerance as a predictor of responses to elevated CO2 in trees,” Physiologia Plantarum 10: 472–480.
5. van der Heijden, et al., 1998, “Different arbuscular maycorrhizal fungal species are potential determinants of plant community structure,” Ecology 79:2082–2091.
Agriculture, the Economy, & Human Health & Welfare:
Policy Issues Relating to Food Production & Consumption
The Earth's Natural History, Global Climate Changes,
& the Future of Human Life & Civilization on the Planet:
Science, Ideology, & Public Policy
Dennis T. Avery, a senior fellow for the Hudson Institute in Washington, D.C., is an environmental economist. He was formerly a senior analyst for the U.S. Department of State. He is co-author, with S. Fred Singer of Unstoppable Global Warming Every 1500 Years.
Avery can be reached at 540-337-6354 or by email to: email@example.com or visit our website: www.cgfi.org
Africa: Black Africa *
Africa: North Africa *
American Government 1
LINKS TO PARTICULAR ISSUES & SUBJECT MATTER CATEGORIES
TREATED IN THE PROGRESSIVE CONSERVATIVE, U.S.A.:
American Government 2 * American Government 3 * American Government 4
American Government 5 * American Politics * Anglosphere * Arabs
Arms Control & WMD * Aztlan Separatists * Big Government
Black Africa * Bureaucracy * Canada * China * Civil Liberties * Communism
Congress, U.S. * Conservative Groups * Conservative vs. Liberal
Constitutional Law * Counterterrorism * Criminal Justice * Disloyalty * Economy
Education * Elections, U.S. * Eminent Domain * Energy & Environment
English-Speaking World * Ethnicity & Race * Europe * Europe: Jews
Family Values * Far East * Fiscal Policy, U.S. * Foreign Aid, U.S. * Foreign Policy, U.S.
France * Germany * Hispanic Separatism * Hispanic Treason * Human Health * Immigration * Infrastructure, U.S. * Intelligence, U.S. * Iran * Iraq * Islamic North Africa
Islamic Threat * Islamism * Israeli vs. Arabs * Jews & Anti-Semitism
Jihad & Jihadism * Jihad Manifesto I * Jihad Manifesto II * Judges, U.S. Federal
Judicial Appointments * Judiciary, American * Latin America * Latino Separatism
Latino Treason * Lebanon * Leftists/Liberals * Legal Issues
Local Government, U.S. * Marriage & Family * Media Political Bias
Middle East: Arabs * Middle East: Iran * Middle East: Iraq * Middle East: Israel
Middle East: Lebanon * Middle East: Syria * Middle East: Tunisia
Middle East: Turkey * Militant Islam * Military Defense * Military Justice
Military Weaponry * Modern Welfare State * Morality & Decency
National Identity * National Security * Natural Resources * News Media Bias
North Africa * Patriot Act, USA * Patriotism * Political Culture * Political Ideologies
Political Parties * Political Philosophy * Politics, American * Presidency, U.S.
Private Property * Property Rights * Public Assistance * Radical Islam
Religion & America * Rogue States & WMD * Russia * Science & Ethics
Sedition & Treason * Senate, U.S. * Social Welfare Policy * South Africa
State Government, U.S. * Subsaharan Africa * Subversion * Syria * Terrorism 1
Terrorism 2 * Treason & Sedition * Tunisia * Turkey * Ukraine
UnAmerican Activity * UN & Its Agencies * USA Patriot Act * U.S. Foreign Aid
U.S. Infrastructure * U.S. Intelligence * U.S. Senate * War & Peace
Welfare Policy * WMD & Arms Control
Africa: Black Africa *
Africa: North Africa *
American Government 1
POLITICAL EDUCATION, CONSERVATIVE ANALYSIS
POLITICS, SOCIETY, & THE SOVEREIGN STATE
Website of Dr. Almon Leroy Way, Jr.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
An Online Journal of Political Commentary & Analysis
Dr. Almon Leroy Way, Jr., Editor