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More Carbon Dioxide is not necessarily good for plants.

Posted on 18 April 2011 by villabolo

An argument, made by those who deny man made Global Warming, is that the Carbon Dioxide that is being released by the burning of fossil fuels is actually good for the environment. Their argument is based on the logic that, if plants need CO2 for their growth, then more of it should be better. We should expect our crops to become more abundant and our flowers to grow taller and bloom brighter.

However, this "more is better" philosophy is not the way things work in the real world. There is an older, wiser saying that goes, "Too much of a good thing can be a bad thing." For example, if a doctor tells you to take one pill of a certain medicine, taking four is not likely to heal you four times faster or make you four times better. It's more likely to make you sick.

It is possible to help increase the growth of some plants with extra CO2, under controlled conditions, inside of greenhouses. It is based on this that 'skeptics' make their claims. However, such claims are simplistic. They fail to take into account that once you increase one substance that plants need, you automatically increase their requirements for other substances. It also fails to take into account that a warmer earth will have an increase in deserts and other arid lands which would reduce the area available for crops. 

Plants cannot live on CO2 alone. They get their bulk from more solid substances like water and organic matter. This organic matter comes from decomposing plants and animals or from man made fertilizers. It is a simple task to increase water and fertilizer and protect against insects in an enclosed greenhouse but what about doing it in the open air, throughout the entire Earth?

What would be the effects of an increase of CO2 on agriculture and plant growth in general? The following points make it clear.

1. CO2 enhanced plants will need extra water both to maintain their larger growth as well as to compensate for greater moisture evaporation as the heat increases. Where will it come from? Rainwater is not sufficient for current agriculture and the aquifers they rely on are running dry throughout the Earth (1, 2).

On the other hand, as predicted by Global Warming, we are receiving intense storms with increased rain throughout of the world. One would think that this should be good for agriculture. Unfortunately, when rain falls down very quickly, it does not have time to soak into the ground. Instead, it builds up above the soil then floods causing damage to the crops. The water also floods into creeks, then rivers, and finally out into the ocean carrying off large amounts of soil and fertilizer.

2. Unlike Nature, our way of agriculture does not self fertilize by recycling all dead plants, animals and their waste. Instead we have to be constantly producing artificial fertilizers from natural gas which will eventually start running out. By increasing the need for such fertilizer you will shorten the supply of natural gas creating competition between the heating of our homes and the growing of our food. This will drive the prices of both up.

3. Too high a concentration of CO2 causes a reduction of photosynthesis in certain of plants. There is also evidence from the past of major damage to a wide variety of plants species from a sudden rise in CO2 (See illustrations below). Higher concentrations of CO2 also reduce the nutritional quality of some staples, such as wheat.

4. The worse problem, by far, is that increasing CO2 will increase temperatures throughout the Earth. This will make deserts and other types of dry land grow. While deserts increase in size, other eco-zones, whether tropical, forest or grassland will try to migrate towards the poles. However, soil conditions will not necessarily favor their growth even at optimum temperatures.

5. When plants do benefit from increased Carbon Dioxide, it is only in enclosed areas, strictly isolated from insects. However, when the growth of Soybeans is boosted out in the open, it creates major changes in its chemistry that makes it more vulnerable to insects, as the illustration below shows.

Figure 1: Plant defenses go down as carbon dioxide levels go up, the researchers found. Soybeans grown at elevated CO2 levels attract many more adult Japanese beetles than plants grown at current atmospheric carbon dioxide levels. Science Daily; March 25, 2008. (Credit: Photo courtesy of Evan Delucia)

Figure 2: More than 55 million years ago, the Earth experienced a rapid jump in global Carbon Dioxide levels that raised temperatures across the planet. Now, researchers studying plants from that time have found that the rising temperatures may have boosted the foraging of insects. As modern temperatures continue to rise, the researchers believe the planet could see increasing crop damage and forest devastation. Science Daily; Feb. 15, 2008.

Figure 3: Global Warming reduces plant productivity. As Carbon Dioxide increases, vegetation in Northern Latitudes also increases. However, this does not compensate for decreases of vegetation in Southern Latitudes. The overall amount of vegetation worldwide declines 

In conclusion, it would be reckless to keep adding CO2 to the atmosphere. Assuming there are any positive impacts on agriculture in the short term, they will be overwhelmed by the negative impacts of climate change.

It will simply increase the size of deserts and decrease the amount of arable land. It will also increase the requirements for water and soil fertility as well as plant damage from insects.

Increasing CO2 levels would only be beneficial inside of highly controlled, enclosed spaces like greenhouses.

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Comments 201 to 228 out of 228:

  1. 200, Eric the Red,

    In the short term, plants have various mechanisms for handling change (such as the way lawn grass browns and goes dormant in the peak summer months, but returns well when temperatures cool and more moisture arrives in fall).

    Over the longer term, however, this causes great stress and begins to kill off plants, and to make them more susceptible to disease.

    At the same time, invasive species that are better able to withstand the conditions will grow, reseed, and push out others (much in the way crabgrass takes over so many lawns by withstanding the summer heat and pushing out preferred grass species that are forced to go dormant).

    In the short term there are some mechanisms (although I question Camburn's increased root mass statement... if temperatures rise or moisture drops so that plants can't take advantage of increased CO2, then how do they have time to build root mass?) that will allow plants to withstand short term changes, but not long term. If the changes are continuous, eventually they are losers and others are winners.

    I can't imagine that evolution will occur to allow plant species to adapt as quickly as simple "migration" wherein plants that are already better suited to the new conditions re-seed and take over where others are failing.

    The end result is massive ecosystem changes (such as the transition of rainforests, like the Amazon, to savanna, or prairie to desert).
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  2. Sphaerica,

    You are focusing all the negatives. What if a temperature rise is beneficial? Not just reduced winter hard freezes, but how many plants will benefit from a general rise in temperature. Add to that the expected increase in precipitation expected with warming temperatures. I am not saying that all this is going to happen, but you seem to think that any change that occurs will be harmful.

    There will be winners and losers in any changing environment. How much of the Earth's environment will change enough to cause your previously described stresses? Granted, plants do not have the mobility of the animal world.
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  3. Eric thr Red wrote: "Granted, plants do not have the mobility of the animal world."

    Yes, which is a very good reason to expect the losers to outweigh the winners.
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  4. EtR#202: "What if a temperature rise is beneficial?"

    Why speculate? From Jump and Penuelas 2005:

    We argue that in fragmented landscapes, rapid climate change has the potential to overwhelm the capacity for adaptation in many plant populations and dramatically alter their genetic composition. The consequences are likely to include unpredictable changes in the presence and abundance of species within communities and a reduction in their ability to resist and recover from further environmental perturbations, such as pest and disease outbreaks and extreme climatic events.

    Or from Colwell et al 2008

    Based on new data for plants and insects on an elevational transect in Costa Rica, we assess the potential for lowland biotic attrition, range-shift gaps, and mountaintop extinctions under projected warming. We conclude that tropical lowland biotas may face a level of net lowland biotic attrition without parallel at higher latitudes ...

    Unpredictable change, more vulnerable to disease and pests, attrition, extinction. Are these how 'beneficial changes' are described? Sure is working out well for coral reef builders.
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  5. And yet, they found, "an abundance of evidence demonstrating adaptation of many populations to their current conditions."

    Changing conditions "may" or "have the potential" to exhibit negative consequences.

    I find it rather interesting that plant life has adapted quite well up until now, but is forecast to face large scale extinction in the future.

    During the past warmer, wetter climate, plant life flourished, but in the forecast warm, wet climate that is not so.
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  6. 202, Eric the Red,

    To add to muoncounter's comment,

    Bark Beetle attacks

    Beetle attacks on drought- and heat-stressed trees are blamed for a massive die-off of pinyon pine (Pinus edulis) in northern New Mexico in the early 2000s. Breshears et al. 2005

    More importantly, why in the world would you assume that plants that are adapted to a particular climate will benefit from any change in the climate, just because you feel like "warm is good"? That is not the case for many plants. Some seeds need winter temperatures to stimulate dormancy. That's how they've evolved. A warm winter may break that evolutionary clock for them. For many plants, increased temperatures will cause them to go into dormancy, awaiting cooler, wetter weather.

    And nothing is predicting more precipitation everywhere. It's changes in precipitation, including too much at the wrong time, and too little other times when needed. It's the expansion of the deserts in the American Southwest and elsewhere.

    The temperature changes will not be uniform. Some areas will experience extreme heat for short periods (that are too long for the local plants).

    Your own desire to see everything through (dying/diseased) rose colored glasses is astonishing. Honestly, how can the facts of plant biology, and even the best case expectations for a changed climate, not scare the bejeezus out of you?
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  7. EtR#205: "During the past warmer, wetter climate, plant life flourished, but in the forecast warm, wet climate that is not so. "

    To what time in the past are you referring?

    And where I sit, the forecast is warm (make that hot) and dry. Sheffield and Wood 2008:

    ... decreases in soil moisture globally for all scenarios with a corresponding doubling of the spatial extent of severe soil moisture deficits and frequency of short-term (4–6-month duration) droughts from the mid-twentieth century to the end of the twenty-first. Long-term droughts become three times more common.

    It would help your arguments enormously if you cited some references.
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  8. 205, Eric the Red,
    I find it rather interesting that plant life has adapted quite well up until now, but is forecast to face large scale extinction in the future.
    Did you really type that?

    Evolution takes millions of years. For every evolutionary winner, there are losers. You see the winners, now, based on past conditions. We are going to abruptly change those conditions... and you think plants are going to instantly evolve/adapt to cope, because you don't recognize that we're changing not just one but almost all ecosystems at a pace that far outstrips almost everything that has ever happened (except in the case of extreme extinction events)?

    Wow.

    During the past warmer, wetter climate, plant life flourished, but in the forecast warm, wet climate that is not so.
    This comment is so ridiculously simplistic and wrong as to be embarrassing to even read.
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  9. Sphaerica,

    If you read the paper to which mouncounter referenced, you will see that many plants have adapted quite well to the current conditions. I never said that all plants will do well. Those which are at the edge of their environmental limit are likely to fair rather poorly. Conversely, there are those which will flourish due to conditions which are beneficial. To think that any change will automaticall be detrimental is what is simplistic and wrong.

    By the way, evolution does not necessarily take millions of years. There have always been winners and losers. Why do you think the losers will outnumber the winners?

    Muoncounter,

    The time several million years ago, when the Earth was full of shallow seas and swamps. It was these plants that many believe became today's oil deposits. Contrast that period with the recent glaciation period. We are currently sitting in between these two climates, and a return to an ice age will not be favorable to many plants.
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    Response:

    [DB] "We are currently sitting in between these two climates, and a return to an ice age will not be favorable to many plants."

    That "return" is becoming increasingly remote.  Recent work strongly points to Business-As-Usual committing us to skipping between 1-5 of the next ice age cycles.

    Note that this research does NOT reflect the results of adding 3.5 to 5.0 Gt of CO2-e methane due to an Arctic methane release nor another 1.0 to 1.5 Gt of CO2-e CO2/CH4 from melting Arctic permafrost.

    Auld Lang Syne, anyone?  Bueller?

  10. EtR - "a return to ice age" is not expected even without human effects for 10,000s of years, maybe 50,000 (see Berger & Loutre 2002 so why bring this up?

    Are you seriously suggesting that adaption of agriculture will occur as easily with current rate of temperature change as it would to changes in the glacial cycle (which are 10x at least slower)?
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  11. EtR#209: "when the Earth was full of shallow seas and swamps"

    You should probably read some geology texts.

    Let's pick one such time, known as the Carboniferous to most of the world (we call it the Mississippian and Pennsylvanian Periods). Briefly, this was a time of widespread shallow swamps, big leafy trees, etc; the result was lots of coal (oil forms from marine critters).

    Abrupt climate change during this time is thought to be the reason for the 'Carboniferous Rainforest Collapse.' You should note that the animal at the top of the food chain went extinct due to this event.

    So my response to all of this glib 'some plants will do better than others; there are always winners and losers'? It's not nice to fool with Mother Nature!
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  12. Eric the Red, there are several facts you are not considering.

    First, evolution is a slow process taking tens of thousands of generations for significant adaptions to occur, and take over the population. That means for plants with an annual life cycle (one generation per year), they are just now becoming adapted to standard holocene (pre-industrial) conditions following the last glacial). For long lived species such as trees, their ideal adaption is for glacial conditions, not inter-glacials. Where it not for the fact that their range has shifted, they would be heavily stressed, and mostly gone extinct. A change in temperature of the same scale as that between glacial and inter-glacial (such as we are currently headed for)will cause them to become even more stressed, or require similarly large changes in range.

    Second, changing range to adapt to new conditions is also a slow process in human terms. For most species of plant, progeny will grow within a few hundred meters of the parent, so the maximum rate of "migration" is a few hundred meters per generation. Given that ranges will need to change by several hundred kilometers to maintain similar climactic conditions, that means most species will take several thousand years, all else being equal, to migrate to a suitable climate zone. With several thousand years of migration required for migration, but several decades for the temperature shift, you should see the problem.

    Three, and most crucially, not all organisms will adapt at the same rate. Some plants are hardy, quick growing and have short generation times. We call them weeds. They are likely to adapt far quicker than other species because of the quick growth and short generation time. Non-plant species, notably insects, will also adapt at different rates. The hardest competition for any species is not the physical environment, but the competition with other species, and consequently difference rates of adaption will result in some species that would otherwise survive becoming very stressed, and probably extinct in some cases. Just such a situation is currently being illustrated by Bark Beetle attacks.

    Because species thrive based on a particular ecological mix, different rates of adaption that disturb that mix are guaranteed to result in a massive loss of biodiversity.

    Your attention is focused on whether CO2 concentrations alone will cause a particular species to become stressed. Well, if it does, then that plant is in trouble. But even if it does not, adaption to temperature change, moisture change, and changing ecological balance will adversely effect most species.
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  13. Tom:
    You are making several assumptions about plants/insects etc that are not correct:
    1. What I write does not apply to trees as my knowledge in that area is limitied at best.
    2. You are making assumptions that plants/insects etc will not adapt quickly.
    a. Example: Plants
    1. Wild oat. There are herbiceds that will kill a wild oat. But even with the best herbicide, a few remain. It only takes approx 8-10 generations of wild oat to establish a strain that is resistant to said herbicide.
    2. Kochia plants.
    They are very robust plants. Extremely small seed, and extremely adaptable. They develop the same resistance to chem as wild oats. And in fact, new strains/biotoa have evolved that are not only resistant to herbiceds, but the requirements for germination have changed. Now we are infested with kochia that will germinate in June/July/Aug. 20 years ago, if you got that flush in the spring....you had 100% control.

    Insects:
    Insects eat plants. Most insects do not consume their host totally, but some do to the point of death. These insects, colorado potatoe beetle as one example, are resistant to most insecticides now. Chem companies have to come up with new combinations annually as within 4 generations, the insect will be immune.

    Plants:
    Plants grow under a host of conditions. Yes, there are optimum conditions, but in reality, they never exist in nature. A plant will grow a long ways away from its optimal growing area. It will thrive and spread. I will use wheat as an example. Wheat is grown in the USA and Canada. The environment on the southern fringe is much different than the environment on the northern fringe. Yet, the plant produces well enough that it is grown for a food stock.
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  14. Tom:
    You also mentioned Bark Beetles. These beetles actually serve a specific function in forests. They eradicate sick trees etc, and thrive on dead wood.
    One of the main reasons for what is considered infestation now is the age of the forests. Fires have been managed, which from a practical environmental look was not a smart thing to do. This practice has almost ruined large tracts of forests because nature demands burns to reproduce healthy trees. In absense of burns, there are natural insect forces, such as the bark beetle that rejuvinate those forests as well.
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  15. Camburn, so when climate zones change (even when it happens slowly), do you see plants adapting? No, only over very long scales. Instead you see vegetation zones move with the climate.

    However, this is sidetrack really from question as whether more CO2 is "plant food". What matters to us really is affect of rapid climate change on our agriculture. I'd say way too soon to draw conclusions yet, but the modelled changes for BAU climate zones suggest caution would be better idea.

    By the way, got a reference for your black beetle hypothesis? I'd like to see comparison between managed and unmanaged forest.
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  16. Camburn @213, your examples of rapid adaption are not relevant because they depend on small (single protein) adaptions that pre-exist in the population, and upon massive (near 100%) mortality rates for variants without the preferred protein. Now if you wish to suggest that most plant species will suffer >90% mortality per generation for 8 to 10 generations in the coming century, your examples are relevant. In the real world, however, plants will be stressed, rather than killed by climate change. And in the real world, adaption will require modification of a number of interrelated biochemical pathways. Hence, in the real world we can expect plants to be stressed for a long time, and to typically take a long time to adapt.

    The problem with stressed plants is that they are less productive, they are more likely to die due to other factors, and they are less able to resist invasive species. The net effect is - and will be - a loss of biodiversity. With the loss of biodiversity, you inevitably have a loss of net primary productivity even once the have adapted and are healthy again, a loss that is only recovered with the recovery of biodiversity which takes millions of years.
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  17. scaddenp:
    This is from memory, but I believe in The Chec Republic some years ago there were massive demonstrations because of the difference in how some wanted to manage the forests.

    Also in talking with cousins up north..Canada...they state that where the forest is young and thriveing, the beetle doesn't really do damage, but the older forests that haven't rejuvinated themselves, the beetle is widespread.
    That is a local observation for what it is worth. I think the thing in Checoslovakia...(spelling)...was much more dramatic and in depth.
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  18. Tom:
    The adaptability of Kochia into sub species....and yes it is actually a new sub species according to NDSU to be able to grow later in the year was/is quit remarkable. This has nothing to do with pesticide, and everything to do with adaptability.

    You are correct, in that vegitation will respond rapidly to a change and adapt. The trees will not be so lucky, as they are a long life species, and their seed does not move as easily as grass/weed/etc seeds.
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  19. Camburn, your example of Kochia and its adaptability is unfortunate. This is a classic case of the kinds of problems that will be exacerbated by climate shifts. Kochia is a declared pest plant in WA because, among other things, it is
    "Notorious for its large size (shading developing crop plants) and its ability to spread fast. Is resistant to insect attack.

    Shoots ...toxic to ... grazing animals, due to high levels of oxalate (up to 4.7% soluble and 11.4% total), nitrate (up to 2.2 percent) and alkaloid (up to 1.2 percent). Plants that accumulate more than 1.5 percent by dry matter of nitrate are potentially toxic."


    There are literally thousands of plant and insect species that threaten productivity of agricultural, pastoral, orchard or market garden activities. The fact that this plant example is one which directly damages both livestock and crops is a mere accident. But it's a perfect illustration of precisely the kind of plant that we'd like to see fail in the evolutionary race being set up by climate change.

    Seeing as weeds, almost by definition, are plants which succeed where they're not wanted, they look to have an evolutionary advantage in many of those environments.
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  20. I fail to see the relevance of massive demonstrations about management of Czech republic forests - all that I am suggesting is that if you have differently managed forests, then you can test the hypothesis. Canada is colder so other factors at work. There is no end to good theories and this might be one, but without supporting data, its just an hypothesis.
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  21. Just been reading this post. I think many commenters are being harsh.
    At the least there is a hypothesis that more co2 will benefit overall plant growth and yields. That hypothesis is not proven or disproven by studying issues with soya beans being attached by a particular beetle etc. It's a much more complex situation that. We do know coal seams were formed during rampant plant growth during high atmospheric co2 periods.
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  22. JMykos: Your last sentence is technically true yet is part of a larger comment that is essentially misleading (all the more so since the key inferences are left unsaid).

    The fact of the matter is that the present climate change is occuring at a rate that is unprecedented in paleoclimate history - with the possible exceptions of periods that we would do well to avoid re-visiting (Paleocene-Eocene Thermal Maximum & the like).

    When you consider also that human agriculture has only developed during the period of relative climate stability during the Holocene, when global climate remained within a tightly constrained range, the above-noted rate of change is hardly encouraging. Nor is it any consolation to look at long-vanished climates, to which our current suite of agricultural crops are not in the slightest accustomed, and marvel at the plant growth apparent.
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  23. "We do know coal seams were formed during rampant plant growth during high atmospheric co2 periods."

    You seem to be implying that coal seams are indicators of high plant growth. However, the requirement for coal seams is an environment which preserves plant material from oxidation combined with low sedimentation rates. The factors favouring preservation are at least as important as abundance of plant source. Plant growth may indeed benefit from CO2 but only if other essentials (especially water) are also unrestricted. It would be a simplistic correlation to equate coal with CO2.
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  24. I am implying that coal seams are indicators of high plant growth with low sedimentation and low oxidation. But back to the topic, which was that high co2 was detrimental to plant growth, and my point was that the breadth of the investigation into soya bean, and only investigating some narrow aspects of the plants issues is way too narrow to disprove that higher co2 overall would be detrimental to the planets overall plant growth. It's some aspects of 1 plant and didn't even mention if the soya grew better or not. It's too narrow to prove or disprove.
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  25. Maybe - important coal seams here are from cool climate peats with quite low plant growth rates. However, the environmental stability allowed them to develop to significant thickness. On the other hand, no amount of CO2 will make many plants grow in the Sahara unless the resulting climate change also brings rain.
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  26. True. I guess you are referring to Canada or Australia during the Carboniferous period.
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  27. JMykos - I agree, a single plant species is not an indication of wholesale issues with agriculture.

    I would, however, suggest you take that discussion over to the CO2 is plant food thread where it is directly discussed, and in the meantime look at such items as Ari's Cool papers 2011 - week 31, where there's a link to a paper showing that regardless of wheat grain mass changes with CO2, the wheat protein content will decrease with CO2 rise.

    There is a considerable literature on the subject - and I personally don't find it encouraging.
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  28. "I guess you are referring to Canada or Australia during the Carboniferous period"

    No, actually I was thinking of Eocene-Miocene coals in NZ. Australian coals are Permian to Jurassic. I associate Carboniferous coals with North America and Europe mostly.
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  29. R. Gates suggested on the Shakun thread that our current fast rise in CO2 (doubling in about 300 years) could overwhelm the biosphere and therefore cause an overshoot in temperature. That will require several things to be true: first that extra CO2 is a net negative for the biosphere; and/or second that rapid climate changes are also net negative for the biosphere; and third that the biosphere changes will exacerbate the temperature rise causing the overshoot.

    I would like to discuss some issues with all three of those. Some studies http://www.biosphere.ibimet.cnr.it/File_Publications/thirty%20years%20in%20situ%20forest%20responses.pdf show that elevated CO2 leads to more rapid juvenile tree growth. Other studies http://www.up.ethz.ch/education/biogeochem_cycles/reading_list/koerner_sci_05.pdf show no net change in mature tree growth. The first study also showed that increased CO2 allowed more drought tolerance and the second has neutral results for the 2003 Western Europe drought.

    For the third item, the biosphere has been modeled for many years to benefit climate models. In this paper http://www.fas.harvard.edu/~eps5/writing_assignment/T_GHG_RECON/bonan_2008_forests.pdf they summarize some basic results: reduced albedo (causing net warming) versus increased transpiration (causing net cooling). I don't see any resolution yet to the question of net climate result. The bottom line is that R. Gates concern is somewhat speculative. The climate may overshoot due, essentially, to desertification. It may undershoot due to enhanced net biosphere growth if the desertification is essentially localized (which I believe it is) and the "warmer = wetter" is the net result for the world (that discussion belongs on a different thread).
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  30. @Eric #229

    I think if you read back through the comments on this thread, everything you say has already been discussed at length. But to summarise...

    Plants have evolved to suit the conditions in which they thrive. This is self-evident when you consider that a plant that thrives in a certain place will often not thrive 10 miles up the road, at a higher altitude, or in a different soil type. So every plant has its niche.

    Given long enough, plants can adapt and/or evolve to suit different conditions. But if everything changes too rapidly then, as R. Gates says, the biosphere could be overwhelmed; for plants are generally at the bottom of the food chain.

    Clearly you can find examples of specific plants in specific circumstances apparently being 'improved' by a change in growing conditions. That's because we're looking at things from a human perspective. When a farmer increases the CO2 in a glasshouse to boost growth, he also monitors all the other things that the plant needs to be healthy: moisture; pests; nutrients; temperature, and so on. And remember he's probably not interested in the plant's ability to reproduce -- it's served its purpose and is in a plastic bag on the supermarket shelves long before that happens.

    So what matters, away from human intervention in the biosphere, is that a plant receives what it's historically received in the location it's growing, and anything that changes -- moisture, temperatures, sunlight, nutrients, CO2 -- is likely to compromise its health. I mean, even water is good for plants -- but too little or too much of it will certainly kill off a lot of them. And a few hundred years is not long enough for most of them to evolve to cope with a changed atmosphere and climate. And as plants fare, ultimately, so do animals.
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  31. Suggested reading:

    “Which plants will survive droughts, climate change?,” UCLA Newsroom, April 5, 2012

    To access this news release, click here
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  32. John Russell, thanks for the reply. Other than my work, I spend the largest amount of my time combatting weeds: mulching, pulling, cutting, planting non-weeds, spraying, and burning (in order of preference). The bottom line is clearly that the biosphere will thrive, see http://tbi.montana.edu/topics/inthenews/pdfsdocs/Science_Stout.pdf for one example and figure 1 here http://research.eeescience.utoledo.edu/lees/papers_PDF/Norby_2004b_NewPhyt.pdf for another. But it won't be pretty. Evolution is slow like you say, but infilling with invasives will happen in a few years in an area where native plants are wiped out by climate change effects.

    My argument is not that this is good (likely not), but that the net biosphere response will not be "overwhelmed" as R. Gates puts it, rather the opposite.
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  33. Eric,
    It is good that you are referencing peer reviewed papers.

    Your first reference shows that some ecosystems have evolved to survive very hot temperatures. How does this limited example show "clearly that the biosphere will thrive"? Your second reference states "demonstrating the reality of multiple-factor influences, and reminding us that surprises can be expected. I read more "surprises can be expected" not the biosphere will thrive. There is also the strong posibility that what thrives will be jellyfish and the tuna will die out. While lots of jellyfish means the biosphere is "thriving" it is not very useful to those who are looking for something to eat. When you cut down rainforest, jungle grows back. It takes decades, or more, for the rainforest to repair itself. If climate continues to change, the rainforest will never come back. If farmers cannot count on an orchard yielding fruit for 30 years they will not plant the trees in the first place.

    Few people expect all life on the planet to die off. It is possible that much of the useful life will die off and all that is left is weeds. Can 8 billion people be fed and housed on weeds?
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  34. michael sweet, I realize now that thrive is not the right word. The vegetative biosphere will grow net and fill in with plants that can grow in more varying and/or stressed conditions. A lot of those plants will be weeds.

    OTOH will a little part time effort I can make 5 acres thrive. Full time with equipment I could do 4-5 times that. That will be repeated worldwide on various scales. I also realize there are millions of acres that won't come back to a productive and diverse state, not just because of climate change as you mention but because of CO2 selectivitity. All the papers I referenced back up the reduction in diversity. They also mostly back up the net growth.
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  35. @Eric #232

    You say, "My argument is not that this is good (likely not), but that the net biosphere response will not be 'overwhelmed' as R. Gates puts it, rather the opposite. "

    It's worth pointing out that R.Gates actually said, "Not only can short-term feedbacks be overwhelmed, long-term biosphere feedbacks might as well" (my bold).

    It's clear that R.Gates was not suggesting -- nor did I assume -- that a rapid increase in CO2 would lead, necessarily, to a die-back of the biosphere. In the worse case though I'm sure you would agree that it could certainly lead to a die-back of life as we know it.

    To my mind that's bad enough. We're playing with fire.
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  36. Eric (skeptic) @234, one aspect you are not taking into account is the succession of regrowth. If you clear an area of forest, the cleared area is quickly colonized by small rapidly growing plants. As years go by they are replaced, first by small woody shrubs and then rapidly growing soft wood trees, and then finally by slow growing hard wood trees.

    In a situation of rapid climate change, large sections of woodland will find themselves left behind by their climate zone and die back. With a pace of change of several degrees C per century, the rapidity of die back will be such that the successor plants will be the small rapidly growing plants, ie, grasses and weeds. These then may be supplanted by woody shrubs, but with sufficiently rapid climate change the climate will change to fast for the full succession (which takes centuries) to follow. The result will be the wide spread replacement of forests by open woodland or grassland.

    Such a replacement will result in a large loss in biomass, both because trees have more mass for a given deployment of leaf area than do shrubs and grasses, and because forests have a layered ecology with a canopy, potentially midlayers, and floor which enhances capture of available sunlight and (hence the lower albedo) and opens up more ecological niches which increases the efficiency of exploitation of available energy.

    This mechanism is medium term only. After a few centuries temperatures will stabilize if only because we will run out of fossil fuels. Once temperatures are stabilized, within a century the normal succession will reassert itself so that biomass will again increase. But the significant loss of forest land for grassland can certainly act as a short term positive feedback on CO2 warming.

    As an addendum I will note two further points. The first is that large scale species loss will result in a loss of specialization in ecologies, ie, a loss of efficiency in exploiting available energy. That will result in a long term loss of biomass, although much smaller than the effect described above. It is probably also a smaller effect than the gain in plant mass due to high CO2. However, (my second point) that gain in plant mass will also result in a loss of albedo in grasslands.
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  37. Thanks Tom. As usual you understand my question and the issues. I agree with most of what you say, but I am not sure if the forest loss will be significant enough to cause a temperature overshoot as postulated by R. Gates. My understanding from figure 1 in my second link in 232 is that the rapid rise in CO2 makes some trees more immune to subsequent temperature increases. The ultimate outcome will be dependent on the uniformity of the tree species and whether they are CO2-selected. In lands managed by the US Forest Service 2.5 million acres are replanted annually out of about 200 million and that can probably be increased significantly to meet new needs.
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