Juan Segarra asks, “Which countries are doing more then the USA in believing in climate change and trying to help to better understand the problems facing it?”
Tom Kimmerer: I think there is a distinction between belief in climate change and taking action. The United States certainly has a lower level of belief in the reality of climate change than most countries, but the majority of Americans (around 67 percent) accept that climate change is real, caused by humans, and requires action. When it comes to actual action, the United States has become a world leader. The recent agreement between the US and China, the declining consumption of oil even as the economy grows, and the upcoming EPA regulations for existing coal plants all suggest that the US is pointed in the right direction. Our responses to date are inadequate to deal with the challenges of climate change and we need to make a lot of progress if we are to avoid a climate disaster.
More broadly, if we look at environmental performance overall, the United States is 33rd among 178 nations, near the bottom for developed countries. The Environmental Performance Index looks broadly at a country’s environmental performance including climate change.
Polly Barnes asks, “What do you think the options are for the defunct coal-fired power plants? Do you think tearing them down is an option?”
TK: A mothballed coal plant is a liability to a utility, but the costs of demolition and environmental mitigation are extremely high. Most utilities have chosen to keep their old plants. If we assume, as I do, that the profitability of traditional utilities will decline as we make the transition to renewable energy. If that is true, the ability for utilities to demolish old plants will decline. At some point, these plants may become a public nuisance and the taxpayers will wind up bearing the costs of demolition and mitigation. For plants in urban areas, the value of the real estate may offset the costs of removing the plants, but I suspect that many plants will remain for a very long time. I will have another column on the subject soon at Planet Experts.
Griffin Mabley asks, “Based on the amount of trees that are cut down every season, are extra christmas trees planted in preparation for the season or is this the natural amount?”
TK: Real Christmas trees can be collected from the forest, cut at a choose-and-cut operation or purchased at a retail tree stand. For Christmas tree farmers, who produce the vast majority of trees on the market, Christmas trees are a crop, planted and grown on land that is often too poor for other crops. Far more trees are planted than harvested to account for loss. Christmas tree farming is one of the most sustainable forms of agriculture, enriches soil and provides income to thousands of farmers. On the National Forests and some State Forests where Christmas tree cutting permits are issued, foresters are careful to keep the rate of harvest well below the number of growing trees.
Jan Ferguson asks, “How long can a tree seed lie dormant and still be viable if it is in a deep layer of earth or rock?”
TK: It is hard to say how long tree seeds last under normal conditions. For trees like oak, the duration is probably only a year or two. For others, such as sugar maple, seeds may lie dormant for decades and germinate upon soil disturbance. Under very dry or very cold conditions, seeds can remain viable a lot longer. A date palm found in an excavation of Masade in Judea germinated after 2,000 years. An herbaceous plant, Silene stenophylla, buried in the Siberian permafrost germinated after 32,000 years.
Chester Whitmore asks, “Do you think we’ll ever run out of oxygen due to there being less and less trees in the future?”
TK: We know that trees produce oxygen and consume carbon dioxide. The majority of oxygen in the atmosphere comes from ancient cyanobacteria, photosynthetic microbes that began producing oxygen about 2.5 billion years ago. The contribution of trees to maintaining the balance of oxygen in the atmosphere is important, but not well understood. And, contrary to what many people think, the number of trees, especially in temperate areas, is increasing, not decreasing. While trees are critically important to addressing climate change and the amount of carbon dioxide in the atmosphere, their role in maintaining the oxygen concentration of the atmosphere is much less direct.
Amber Nash asks, “How has the ancient Bristlecone Pine continued to live? I’ve visited them, [and] where they are seems so unlikely for them to survive.”
TK: I agree that the bristlecone pine habitat is very harsh. The trees look like they are declining but have looked that way for thousands of years. The habitat of the White Mountains (California) is dry, low in fertility and very cold. Oddly , these are the conditions that lead to very long life in many trees. Within a tree species, good growing conditions (high soil fertility, adequate moisture, long growing season) is associated with rapid growth but shorter lives. The longest lived trees are the ones, like bristlecone pine, that grow in the poorest habitat. There are probably specific physiological adaptations that allow these trees to have long lives, but the poor environment is an important contributing factor. Climate change is accelerating the growth of high-elevation bristlecone pines, and this is likely to reduce their longevity.
Josh Guisinger asks, “In rural Ohio, coal mining has left numerous types of contaminated soil situations. Acid mine drainage, as well as coal byproducts, litter the landscape with ‘dead zones.’ These ‘dead zones’ are running/standing water, as well as previous forests, which only support minimal life. Since different types of algae and mosses thrive in these environments, is there hope for a tree species that would also flourish in these types of environment? And do you think that the tree species that are affected by this type of environment are affected by the contamination, or just the mass disruption of viable soil, or both?”
TK: When discussing recovery from coal mining, we have to draw a line between mines (surface or deep) created and abandoned before 1977 and those created after 1977. In that year, SMCRA, the Surface Mine Control and Reclamation Act, was signed. After 1977, surface mines were required to “reclaim” the land. This was a disaster. The heavy equipment and grading methods used compacted the ‘soil’ and prevented the growth of trees. Many surface mines have stayed in herbaceous plant cover for over 30 years. More recently, exemptions to the original SMCRA have allowed reforestation of a few sites.
For mines abandoned before 1977, trees become established and often grow very well. The highest site index for white oak in Ohio is on an old surface mine (site index is a comparative measure of growth of a particular species on different sites – higher site index means faster growth). However, as your question points out, acid mine drainage and coal “hot spots” can prevent anything from growing. Virginia pine in association with the mycorrhizal fungus Pisolithus tinctorius, often will grow on these acid sites when nothing else will. Given enough time, the Virginia pine will mitigate the acid hot spots and eventually other trees will be able to grow there.
These abandoned sites often require extensive rehabilitation. Since the original owners abandoned the land, state and federal agencies have to take the lead in reclamation, Reclamation of abandoned lands is funded by a tax on existing mines. However, funds are inadequate and recovery is slow. Ironically, though, these lands will probably recover better than post-1977 surface mines.
Justin Sims asks, “Do trees in one region affect climate in another (e.g. do Brazillian rain forests affect North America’s climate)?”
TK: Absolutely. Tropical forests create their own climate. Rain doesn’t create rainforests as much as rainforests create rain. Tropical moist forest have important impacts on the global water cycle and carbon cycle. As one example, a NASA study showed that deforestation in the Amazon affected rainfall in the Gulf of Mexico, Texas and Mexico. Since rainfall in the Gulf of Mexico has a powerful affect on southern U.S. weather, it is likely that the effect of deforestation in the Amazon is felt throughout the U.S.
A new study by Deborah Lawrence and Karen Vandecar of the University of Virginia came out on December 18 and shows that the effects of tropical deforestation on worldwide weather is large and severe. Deforestation causes warmer, drier conditions locally, and this local effect may be felt globally. Specifically, the project found that tropical deforestation could reduce midwestern U.S. rainfall and increase rainfall in the United Kingdom. The study appears in Nature Climate Change.
Landon Smith asks, “Through gene selection and manipulation humans have increase yields on crops. Is such research occurring on tree species to increase growth speed to help replenish forests?”
TK: Forest genetics and tree breeding are an important part of ensuring our future supply of wood and other forest products. There is a big difference between breeding trees and breeding crops: crop production is increased by inbreeding, combining genes from closely related plants and reducing the genetic diversity of the crop; tree production is increased by outbreeding, combining genes from a wide diversity of trees and increasing the genetic diversity of the crop.
For example, it is well known that the genetic diversity of a loblolly pine plantation in a breeding program is higher than the genetic diversity of a natural loblolly pine stand. In this sense, breeding trees is like breeding horses – everything possible is done to avoid inbreeding. Simply put, inbreeding is fatal to trees, but is required in crop breeding. Yields of genetically improved loblolly pine are three times the yields of wild trees, even though we have only been breeding loblolly pine for about 70 years.
Guy Meilleur asks, “[Regarding] natural form, how does the architecture of trees (as identified by Halle, Roloff, Pfisterer et al) inform their management? For example, some genera form pronounced or slanted branch collars; others are small or very longitudinal. So can there be one rule for pruning all trees?”
TK: The form of trees is under very strong genetic control. That is why you can recognize an open-grown sugar maple or American elm from a great distance. Under forest conditions or stress, form is modified by environment. For example, a forest-grown sugar maple has a crown that is as much a result of light competition as it is of genetic expression. For open-grown trees that are the concern of many arborists, it would be very smart to prune (when necessary) in accordance with the natural architecture of the tree. However, the majority of arborists do not know enough about tree architecture to do this properly. I would hope that the arboriculture industry would start paying more attention to architecture of trees, but this may be too much to ask.
Hen Saveourwoods asks, “Should we in the UK stop planting Ash trees for forestry? If so, what tree/s could replace the Ash?”
TK: No, you should not stop planting ash. There are almost no tree diseases for which there is no resistance – American chestnut being the rare exception. Searching for Chalara-resistant trees and collecting their seeds is ongoing in Britain and needs to continue. Similarly, selection for resistance is important with other tree diseases such as white pine blister rust of whitebark pine. It is expensive to identify and propagate resistant trees, but it is far cheaper than losing a species. Europe has much lower tree species diversity than North America, and you certainly cannot afford to give up on a species. You are likely to be hit with the double problem of Chalara and emerald ash borer, but that is all the more reason to redouble efforts to select and breed for resistance. The good news is that the majority of new pests and pathogens eventually become less serious over time as susceptible individuals are selected out of the tree population and as natural enemies of the pest or pathogen increase in populations.
Jill Butler asks,
- “Is there a relationship between the amount a tree is light-demanding and how much shade it creates? Fagus sylvatica is very shade tolerant but is also very shade giving; pinus sylvestris the opposite; but Frasinus excelsior is quite shade tolerant but not very shade giving.
- What is the ‘natural’ form of a tree? Open grown? Or what is the opposite term ([it] can’t be ‘forest’ form as the term ‘forest’ used as dense canopy is very modern)?
- What shrubs can flower and fruit under 50 percent shade cover or greater?”
TK: This is a complicated set of questions that are hard to address fully in less than a book-length reply, but let me give a few simplistic answers. In general, shade-intolerant trees have less complex crown structure than shade tolerant trees, and they don’t maintain populations of shade leaves in the lower crown. A tolerant tree will have both sun leaves in the upper canopy and shade leaves in the lower canopy. So a shade-tolerant tree like beech will absorb more of the incident light than an intolerant tree. There are some exceptions that make this a complex issue. For example, many of our woodland pasture trees are quite shade tolerant when young but less so when mature.
As in the question about tree form, the genetic expression of the shape of a tree is only obvious when the tree grows without competition. In a forest, the form of the tree is a product both of its genetic potential and the environmental effects of competition for resources from other trees. Rather than referring to the “natural” form of a tree, which is hard to define, we can say that the form of a tree is a result of its architecture, which is genetically determined, and its environment, particularly with respect to competition from other trees.
The effects of shade on fruiting depends on the intrinsic (genetic) shade tolerance of the species. An intolerant tree like sumac will not flower or fruit in shade. A very shade tolerant tree such as pawpaw will flower and fruit in moderate shade, but may not do so in deep shade. Knowing which shrubs will perform well in shade requires a pretty thorough understanding of the natural history of each species, and I don’t know European shrubs well enough to comment.