PeopleSystems and Sustainability: This Week in the Global Environment
Ecologists make their way into some obscure corners of the biosphere. Examples? How about the study of Mural Vegetation, in this case “Mural” meaning “wall”? There is indeed an active, if small, community of researchers who study the ecosystems of vertical surfaces, most (but not all) of human origin. Another is fossil cave dung. Much has been learned by deconstructing and reconstructing the ecology of fossilized ground sloth dung, and the debris piles left by rodents in certain caves, mostly in South America but also in Africa. And human commensal invertebrates have a technical following. Did you know that there is at least one species of nematode found only in beer mats in German bars? And that about 75% of human beings are colonized by “eyelash mites”, tiny arthropods that live at hair follicles and apparently survive by absorbing nutrients from the semi-liquid goo generated at the root of the hair.
But we could do this for page after page. One seemingly obscure aspect of the biosphere that has been favored for study sporadically over the decades is aerial plankton. I turns out that the atmosphere is populated by an amazing abundance and diversity of microscopic life. Recently, Popular Science provided a brief report on aerial plankton surveys conducted by researchers at the Georgia Institute of Technology in Atlanta, GA, USA (fair disclosure: my youngest son is a student at Georgia Tech). You can find summary information at http://m.popsci.com/science/article/2013-06/bacteria-33000-feet . Basically, by filtering air while flying at 6 miles altitude, investigators determined that about 20% of the total particles were not only biological in origin, they are living cells! The atmosphere is not purely a physical and chemical phenomenon. It is biologically active, and linked in potentially important ways to other components of the biosphere. For example, among the cells identified, E. coli bacteria are present. Likely swirled into the atmosphere by hurricane cells over cities, it might well be the case that diseases are spread over vast distances by aerial plankton.
Since any atmospheric particles are associated with weather, clearly bacterial aerial plankton play a role—unquantified and uncharacterized to date—in determining weather conditions. It is possible that there is a functional nutrient cycling in situ, affecting the chemical composition of precipitation and therefore its quality and quantity.
Without much more investigation (particularly hypothesis generation and testing), it is impossible to say whether or not aerial plankton is more than an inert oddity. But at the biomass and diversity levels reported by the Georgia Tech researchers, this seems unlikely. It appears to me that there is much potential for important processes, unknown to date, to be occurring at high atmospheric altitudes.
I encourage you all to formulate some working and testable hypotheses next time you find yourself cruising at high speed and high altitude on your way to a technical colloquium, project meeting, vacation and R&R, whatever. This is one of the few remaining scientific endeavors to which meaningful contributions can be made simply by thinking. Take advantage of it when you can!
PeopleSystems and Sustainability: This Week in the Global Environment
Lions and Tigers and…Ants, and Enzymes, and Bacteria, and… .
Leaf-cutter ants of the genus Atta are among the most fascinating and complex creatures on earth. Actually, Atta themselves are unable to live simply as “creatures”. They require an enormous and enormously complex ecosystem, managed carefully and constantly, to survive and prosper.
Wood-“eating” insects, of course, lack the enzymatic ability to digest and process lignin and cellulose, putting wood off-limits as a direct food source for various roaches, beetle larvae, termites, and ants. Rather, they have a gut flora of microbes that CAN process wood into digestible and nutritive biochemical subcomponents.
Atta ants operate differently from “conventional” wood-degrading insects. Rather than relying on their gut flora, attines use external fungi to break down cellulose and lignin in large underground nests. The nests contain extensive chambers that serve, in a quite literal sense, as farms. The ants cut leaves into appropriately-sized pieces, carry them into the farm chambers, add them to the growing fungal/leaf complex, and then work to maintain the farm chambers. Humidity is carefully controlled, wastes are removed, and the nutritive fungal products are harvested to maintain the metabolism of the entire colony.
Recently (http://www.sciencedaily.com/releases/2013/06/130614125647.htm) researchers at the University of Wisconsin-Madison have developed an understanding of Atta farms that reveals far more exquisite complexity than was previously known. It turns out that the ant-leaf-fungus system is insufficient for long-term sustainability. Previously unsuspected bacteria appear to be necessary for the system to operate in the long haul.
And operate it does. Atta process enormous amounts of vegetation, and their colonies reach enormous sizes. The biomass and metabolism of Atta colonies can be dominant herbivores in areas where they occur in high density.
When I was in school, I worked on whole-system agroecosystem study projects at the University of Georgia Institute of Ecology. I am not an agronomist, I’m a systems ecologist and field biologist. The lesson I took from the agroecology studies might have differed somewhat from those the agronomy folks took. I realized that the agroecology minimum-till fields needed the entire ecological complex to be present, accounted for, and operating for the system to operate at its fine-tuned best. This means such seemingly peripheral organisms as birds, small and medium mammals, even herbivorous insects, usually a “problem” in farming, were necessary for the agroecosystem to function.
The work from UWM, it seems to me, reinforces this and should be taken as a lesson for human agroecosystems of all kinds. Properly functioning microbiota can cycle positively into soil-producing and maintaining arthropods, which help support herbivores, which help assure that the crops grow when, where and how they are needed. This is true if the agroecosystem is maximum-tillage, full irrigation, artificially fertilized, or if it is small-scale, locally fertilized, minimum tillage, low-irrigation, low fertilization.
The biosphere is not simple. Components of the biosphere—agroecosystems—are not simple. This makes it tough for us to study them effectively. However, it DOES contribute to (my) belief that components of the biosphere are robust. They are not sensitive, likely to collapse, constantly under pressure, always at risk. They have redundancy, resiliency, and, if managed as carefully as those operated by Atta ants, likely to be highly sustainable.
Or perhaps I’m over-optimistic. But I don’t think so. We live in a robust biosphere. If we handle it effectively, it will last us for a long time. And can not only contribute to our food supply, but our energy as well. The future looks bright to me. Brighter in the context of the underground farmers, the Atta ants.
PeopleSystems and Sustainability: This Week in the Global Environment
Maybe It IS Easy Being Green
Early debates (going back more than a decade now) regarding the potential impacts of global warming were backed up by ecological simulation models of primary production and plant biomass that ignored a key factor—carbon dioxide limitation of much of the vegetation in the biosphere. Recently, more sophisticated models have incorporated this parameter in one form or another, providing what are likely to be seen in retrospect as more accurate, precise, and well-calibrated projections of climate change effects.
This week, Science Daily (http://www.sciencedaily.com/releases/2013/05/130531105415.htm) presented a synopsis of work conducted by Randall Donahue and colleagues at the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO) and published in the Geophysical Research Letters in which the authors attempted to sort out a signal of carbon dioxide increase from the “noise” of the many parameters, such as temperature and moisture affecting plant growth.
The exercise was far from straightforward. Donahue and his people concentrated on arid areas where increased “green” could be quantified by contrast to the dry substrate (as opposed, say, to tropical or temperate forests where leaf cover already exceeds 100%, making remotely-sensed increases in leaf area impossible to ascertain). They established site-specific indices of maximum “green” attainable via a three-year moving average of moisture changes. Then they quantified green exceedances of the index, likely indicating the effect of carbon dioxide fertilization on the landscape.
One thing the authors did not comment on is the fortuitous high value of forcing their work into arid regions. Desertification is one of the greatest environmental problems we face today. If carbon dioxide fertilization can, even incrementally, slow or reverse desertification in key areas of the Sahel, central Asia, the Americas, and even Australia, it will be an enormous boost to the ecological quality of the biosphere. At the same time, it will feedback on human quality-of-life, offering reduced hardships in regions traditionally among the most challenging places for people to live.
I suggest we all take a deep breath and re-read the cover of our copy of The Hitchhiker’s Guide to the Galaxy, where it reads, in soothing green letters, “DON’T PANIC”. As scientists and environmental managers, it is critically important for us to be objective, to sort the good and bad effects of global climate change, and incorporate those in our communications to politicians and the public. In this case, CSIRO scores one for the good guys. Climate change may help truncate desertification. Time to tackle other items on the impact assessment list. But those are subjects for subsequent columns.
