Drs. Lew Ziska of the USDA Agricultural Research Service and Jeff Dukes of Purdue have just published a significant new work entitled Weed Biology and Climate Change. (Yikes - it is 149 simoleons! Wiley-Blackwell, have you no shame?! At least they have the decency to publish an interview with the authors... Let's hope the message gets out there}.

Our efforts to control the environment to advance human well-being are characterized by the creative use of energy to increase our ability to work, and by harnessing nature through agriculture to produce food more abundantly than is provided by nature. These two major civilizing trends have run head on into one another with climate change. Our preferred energy source, fossil fuels, release carbon into the atmosphere, creating changes that in turn affect our ability to farm. If we are to avert simultaneous food and energy crises that would threaten to bring many communities to their knees, we need to be at the top of our game. This book represents the kind of science we need to understand and act on.

The Agricultural Research Service is one of those federal agencies potentially on the chopping block (see http://washingtonexaminer.com/blogs/beltway-confidential/2011/01/detailed-look-rand-paul-spending-bill). People, let's not cut off our nose to spite our faces!

Amplify’d from wisciblog.com

Weed Biology and Climate Change

In a nutshell, what are the most significant ways climate change is affecting weed biology?

ZISKA: Weeds are supremely adapted to change; they thrive on environmental disturbance. Therefore, sudden changes in temperature, CO2, drought, floods . . . in short, all of what we anticipate with global climate change, increase ecological “opportunities” for weed seed dispersal, initiation, and biological success.

ZISKA: There are some weeds that are universally recognized as being harmful in almost all circumstances (e.g. puncture vine, nightshades, poison ivy). That being said, there are many plants that are undesirable simply because we haven’t found a use for them. For example, wild or red rice is an acknowledged weed in rice production, but may also have unique genes that will allow it to survive in extreme environments—genes that may be very useful in adapting cultivated rice to climate change.

Do you anticipate that climate change will impact all growing environments, even down to amateur gardens? If so, what sort of advice would you give to non-scientists for dealing with this issue?

DUKES: Yes, it already has. I was in England a few years ago and got to visit some gardens where Robert Marsham and his ancestors had been tracking the flowering dates of a variety of plant species since 1736. Keeping track of flowering times and the timing of “signs of spring” is a pretty common hobby there. Plants in that region are now flowering, on average, something like a week or two earlier than they ever did before over that time span.

So, yes, climate change has already altered growing environments in lots of ways. But it’s not something that would be obvious to anyone over a period of a decade; there’s too much year-to-year variability for people to notice trends over that sort of timespan. And it won’t change peoples’ day-to-day activities much, but they may be able to consider planting some species now that they wouldn’t have considered a few decades ago.

ZISKA: If you want to see, in a simple way, how climate change has altered amateur gardening, just look at how plant hardiness zones (the different colors on the back of a package of seeds) have changed since 1990. Read more at wisciblog.com

The Sustainable Cities Collective blog carries a post today about a German effort to identify the trees most likely to thrive in tomorrow's environment. Obviously, models show different conditions for different places. What trees will thrive in African cities, for example, where they often provide essential shade and shelter?

It is issues like this that are likely to be overlooked when we think about climate adaptation. Without people of vision like Klaus Körber, no one will pay attention to trees until theirs are dying, at which point it is a little too late to plan.

Philips, the electronics conglomerate, has a competition underway for its "Livable Cities" award. One of the finalists, James Kitoya, proposes creating 45 ‘Shade Stands’ across Uganda’s capital, Kampala, to provide such shelter. (Sadly, it is running last in the voting).

The streets of Bobo Dioulasso, Burkina Faso, are lined with shade trees. Photo courtesy of Guillaume and Pauline via Flickr, licensed under Creative Commons with some rights reserved (non-commercial use only, attribution required, no derivative works).

 

One thing that troubles me about the discussions of good tree species to use is that there doesn't appear to be any thought of invasiveness. For example, in the Sustainable Cities Collective article, Ailanthus is mentioned as a very "resistant" species. Is Ailanthus the tree of the future? Perhaps, but let's not make it a self-fulfilling prophecy just yet - it is highly invasive and corrosive to natural systems in North America (evidently less so in Europe). It undermines the resiliency of natural habitats by replacing a diverse system with monotypical stands (it is allelopathic). Nothing grows under it, it is almost impossible to eradicate, and it colonizes quickly (in Washington DC it is called the "ghetto palm" because vacant lots in the inner city quickly fill with the palm-like shoots of this rapidly growing tree species).

So to plant Ailanthus is in a sense to opt for the "nuclear option". Not to say it isn't the right choice - but it is important to chose deliberately and carefully and to know what you're getting, because there's no turning back.

What other features contribute to resilient cities that are being overlooked?

 

 

Amplify’d from sustainablecitiescollective.com

"Climate change will not leave the green lungs of our cities untouched. We already know that some species will not get along with the associated weather extremes in the long run, "said Klaus Körber of the Bavarian State Institute for Viticulture and Horticulture in Veitshöchheim, Germany.

With the predicted increase in extreme weather events the following aspects have to be considered more in the selection of trees: • a firm fastening in the ground by a strong root system, • the danger of wind damage and falling branches, • the regeneration by shoots after storm damage and • an extensive root system to prevent soil erosion.

Another important aspect: drought stressed plants are more susceptible to disease. "With the globalization of trade the infestation of plants with new diseases and pests is enormous. Previously robust, local species can be infected, too, "said Körber. According to the expert, it must be the goal, not always put on the same five or six main tree species, but to increase the diversity. "Only a broad base of suitable plant species and varieties reduces the risk that more new diseases and pests reduce the available range." With this claim there have been problems in the past by the debate on nature conservation and autochthony. Also exotic, recommended species and varieties often weren’t available in the nurseries because there was little reliable demand from the municipalities. "For the city trees of the future, it will not be about which species have been growing here before, but what types thrive right under the changed conditions and work good as the green lungs of our cities in the long run," stressed Körber. "And for the nursery the change to new species on the one hand is a challenge, but on the other hand, it’s a great opportunity!"

Extremely resistant to the urban climate are trees such as Ginkgo, Gleditsia Tree-of-heaven (Ailanthus), Honey Berry (Celtis australis), Turkish Hazel (Corylus colurna) and Sophora. "But from past experience one shouldn’t not put too much on such exotica,” Körber stated. “First, in their homeland a number of diseases and pests exists that could follow their hosts. Second, there are significant differences between cultivars with respect to the resistance, too. Third, the growth form in some cases doesn’t meet the requirements of a street tree." Generally, the proportion of a certain tree species in a city should never be too high. Read more at sustainablecitiescollective.com

The link between global warming and the spread of invasive species is real.  But authorities responsible for food security and natural resource management are either unaware of the linkages between  invasiveness and climate change, or are aware of the  linkages and view that the science as inconclusive. Not enough  attention is being given to the potential risks to food systems, water supply, energy production and biodiversity as a result of climate change.  And no climate model considers the impact of weeds on crop yield in the face of climate change.

Plants can respond to climate change in several ways; temperature, precipitation, available light, and CO2 levels all affect plant growth patterns.  Plants are adapted to different environmental conditions, and the composition of species will change according to the combination of climatic factors.  90% of all living matter consists of plant life, so a perturbation in plants due to climate has potentially broad ramifications for ecosystem services and life support systems.

Presently, 96% of all plant species lack optimal CO2.  All plants do not respond equally to elevated levels of CO2, however.  Plants with C4 photosynthesis are more efficient users of existing levels of CO2 and will not respond as well to elevated CO2 levels as will plants with C3 photosynthesis.  Initial evidence suggests that in elevated atmospheric CO2 levels, C3 weeds could be preferentially selected, potentially resulting in weed species dominance and concomitant reduction in crop yields. Response to CO2 is independent of nitrogen requirements, meaning that more efficient users of nitrogen may be better able to take advantage of elevated atmospheric CO2.  Elevated atmospheric CO2 levels will favor vegetative reproduction (rhizomes, runners or stolons, suckers, bulbs corms etc) over sexual reproduction through seeds and spores; weedy vines can be expected to become an increasing problem.

Rising minimum winter temperatures are expected to reduce the range of some species and expand the range of others.  In temperate climates, this will favor invasive weed species.  

CO2 increases biomass of some invasive weedy plants.  In temperate regions, the range of invasive weedy plants will expand.  The implications of more invasive plants over a wider range include:

• potential for increased evapotranspiration

• potential for increased fuel loads and risk of wildfire

• reduction in crop yields due to increased competition

loss in biodiversity due to increased competition, changes in  wildlife habitat affecting climate-sensitive species

Not only can CO2 result in reduced crop yield and water loss due to weeds, but the ability to control weeds is itself impaired.  The efficacy of glyphosphate, an important agricultural herbicide for weed control, is reduced as CO2 increases.  Mechanical control will be problematic when conditions favor vegetative propagation that can be enhanced through mechanical disturbance.

Adaptive management is needed.  Models must be developed for land managers and new management strategies produced in consultation with stakeholders.  Early warning systems can aid in effective responses to biological invasions, but investment in control and management of invasive weed species is necesssary. In some cases, control of such species could include biomass energy applications, creating new opportunities.  All this requires additional investment in science, management tools, and public information.

Much attention has been given to hazard reduction and disaster response in view of changing climatic conditions.  With the exception of the role of ecological resilience as a mitigating factor in natural disaster, the biological dimensions of climate change have been largely ignored.  But the biological dimensions extend far beyond the response to acute episodic events such as storms, floods, fire and drought.  The biological dimensions that are chronic and persistent, in the form of changing plant communities and plant behaviors, have the potential to undermine food security, health and water supply.  To be comprehensive, adaptation measures must better address impacts on plants.

(photo: invasive vines causing deforestation of the interior of Rarotonga, Cook Islands. Photo credit: John Waugh, use with attribution authorized).