The Silent Underground Network
Under your feet in the woods is a vast communication network
where information technology keeps the ecosystem functioning.
Ecology deals with the interactions of different species. While most biologists study single organisms in depth, some look to how a field of organisms functions together, in a meadow, forest, desert, or other biome. The more ecologists learn about these living communities, the more they are astonished at their sophistication.
The dirt on dirt: That’s the headline in a National Geographic article about a dirty subject: “5 things you should know about soil.” You may not think it worthy of a UN “World Soil Day,” but all humans depend on the quality of topsoil for our food. In a short video, soil scientist Jerry Glover reminds us that “The minerals, the nutrients that make up our muscles and bones almost entirely come from soil.” Maintaining the quality of soil, therefore, is an investment in our own health. It also helps prevent droughts, famines, and dust storms. Glover is joined by David Montgomery, who wrote—well, not a dirty book, but—a book on dirt, specifically about the impact of poor soil on ancient civilizations.
Chemical fertilizers, which replace three or four nutrients, are simply not enough to replace the complex system that is soil. They’re “not a full health package,” says Glover.
That’s because soil is crawling with microbes and bugs, which nourish the soil. They help cycle nutrients in exchange for plant sugars. It’s a symbiotic relationship that is the root of life, but we don’t fully understand it, according to Montgomery.
Glover calls the life underground “the other half of life,” and comments that it’s only been in the last 30 years or so that we have begun to appreciate all that soil organisms do for us.
Word of the day: vermiculture: Earthworms are the subject of a PhysOrg article showing hands holding soil permeated with worms. We usually don’t think about earthworms except when digging for fish bait or finding them splayed on the sidewalk after rain, but earthworms are important to life. They are “nature’s free fertilizer,” the article says. Farmers have known for centuries that earthworms increase crop yield. A team at Wageningen University wanted to quantify that benefit:
The overall outcome of the study was very clear: “On average, earthworm presence increases crop yield by 25% and aboveground biomass by 23%” says Ingrid Lubbers. “We also found that earthworms did not change the nitrogen content of plants, indicating that crop quality was unaffected. Earthworms therefore have a strongly positive effect on crop production.”
Worms don’t create nitrogen, but they make it available by unlocking it from biomass. They work better if you supply biomass for them to work on, and worse when you apply nitrogen fertilizer. Interestingly, poor soils saw the most benefit with vermiculture, the practice of “worm ranching” for increasing soil health.
The microbe network: Earthworms are just the larger members of a whole network of underground organisms. A review article in Nature, “Belowground biodiversity and ecosystem functioning,” by Bardgett and van der Putten, takes a look at how they work together. They begin by recognizing the renewed interest in soil in recent years as scientists grasp that “belowground biodiversity represents one of the largest reservoirs of biological diversity on Earth.”
Soil communities are extremely complex and diverse, with millions of species and billions of individual organisms being found within a single ecosystem (Table 1), ranging from microscopic bacteria and fungi, through to larger organisms, such as earthworms, ants and moles (Fig. 1). Our understanding of this hidden biodiversity is limited, at least compared to what is known about aboveground diversity. But the last decade has witnessed a growing number of studies testing how belowground communities are distributed in space and time, how they respond to global change and what the consequences of biodiversity change are for plant community dynamics, aboveground trophic interactions, and biogeochemical cycles.
Underground economy: One interesting change in thinking arising from increased interest in soil science is seeing the belowground community as a cooperative, rather than a competitive enterprise: “new mechanisms are being proposed, such as the notion that the rhizosphere [soil community] is a market place where roots and symbionts exchange carbohydrates for nutrients where co-operation can be rewarded, whereas cheating may be discouraged.” It’s not that the organisms have brains to think about this, but their pushes and pulls work out to create a harmonious “soil biostasis” something like the dynamic equilibrium within our own bodies. This is partly accomplished with the exchange of chemical signals, and with partnerships where cooperating members all benefit. So far from a Hobbesian “war of all against all” underground, we might picture the soil community as a system of separation of powers and checks and balances, allowing the “market place” of beneficial exchange to flourish.
Update 12/22/14: Cryptobiotic soil ecosystem rivals rainforest: Astrobiology Magazine has an article about “biological soil crusts” or cryptobiotic soils, those crusty, raised mounds often seen in dry deserts. They house an “incredibly diverse” population of small organisms that nourish each other.”Life forms including bacteria, algae, fungi and lichens, as well as plants such as mosses and liverworts, can band together to create biological soil crusts in dry, nutrient-starved environments,” the article says. “Scientists are just beginning to document the diversity of species that call biological soil crusts home.” Microbes with flagella live in these dry-looking, crusty mounds; “these scruffy stretches can house delicate ecosystems as varied and complexly interwoven as that of a lush, tropical rainforest.“
Plant detox: Two articles show how certain aboveground plants can improve underground health. Willow trees, the University of Eastern Finland reports, are “cost-effective cleaners of contaminated soil.” Planting willows has other benefits, too: “Furthermore, the wood biomass grown in the process can be used for energy production and as a raw material for biorefineries,” a professor says. What about arsenic? Can plants detoxify that? A paper in PLoS Biology says yes: Robin Meadows reports on a gene named HAC1 (high arsenic content gene #1) that converts dangerous arsenate, which mimics vital phosphorus, into arsenite that can be released back into the soil. For those living in high-arsenic soils, this has “tremendous potential to benefit human health,” Meadows says, by aiding agronomists in “developing crops that can be grown in high-arsenic regions and still be safe to eat.”
The bugs that ate New York: In other ecology news, researchers found that vermin, including ants, millipedes, and other insects work like urban clean-up crews. “Bugs in Manhattan eat thousands of kilograms of trash each year,” Science Magazine says. They don’t get it all, but what they do clean up is non-trivial, albeit modest. Surprisingly, the bugs work harder in the concrete jungles than in the parks, consuming 600 to 975 kilograms of waste a year—the equivalent of 600,000 potato chips.
Can ecosystems evolve? A short article by Elizabeth Howell on Astrobiology Magazine, “How did complex life evolve, and could it happen elsewhere?” ponders the origins not of single cells but ecosystems. As usual, there are more questions than answers among evolutionary astrobiologists. Frank Rozenzweig (U of Montana) is seeking answers to “such as how do the genetic ‘starting point’ and ecological setting influence the tempo and trajectory of evolutionary change.” One thing is for sure: they’re not going to find answers at Titan where some astrobiologists are looking. It’s almost 300 degrees below zero out there.
What’s wrong with humans? Two sad stories show that there is something amiss in humanity. Studies in New Zealand show that early human pioneers single-handedly pushed out the islands’ megafauna, including all the giant moa birds. The extinction was “incredibly rapid when humans arrived,” PhysOrg says. Another tragic story is happening in our time: poaching of rare rhinoceroses is up 30-fold over the past 13 years, PhysOrg reports, and is currently out of control. Poachers kill the rhinos for their horns in the mistaken belief in some cultures that powdered rhino horn has medicinal properties (its just keratin, the same material in fingernails). That mistaken belief, and the rarity of rhinos, has turned the horns into something as valuable as gold to them, driving the poaching market. Sawing off the horns in advance has not worked. Conservationists are at a loss what to do. Elephants, similarly, are in danger because of demand for ivory in China. Poaching is “out of control” there, too, PhysOrg says, worrying conservationists that elephants could be driven to extinction in a generation if solutions are not found.
It is frustrating and tragic that humans cause such damage to God’s creation. Mankind was given dominion to manage the ecosystem as good stewards, but instead, due to ignorance and sin, we drive species out of existence. It’s not as simple as that sounds, because we try to eliminate Ebola and smallpox, too, for the good end of saving human lives. But rhinos and elephants are magnificent animals whose horns and tusks are part of their greatness; nothing is gained by killing them off; it will be like killing the goose that lays the golden egg. Selfishness doesn’t think long term, but only for the benefit to “me” if I get a fake medicine from rhino horn. These people could get the same fake benefit by grinding up their fingernails. Each animal has its place in the ecosystem. We often don’t learn about their benefits till they are gone, like the history of Yellowstone shows when the wolves were driven extinct. We’re not trying to be simplistic here; the concerns of ranchers need to be heard and their interests protected. Animals need to be managed, not eliminated entirely. It’s a shame there are no more moas to see in New Zealand. Most of the large post-Flood (Pleistocene) mammals are gone, too; theories waffle about whether humans drove them to extinction, or they perished in changing climates, like the Ice Age. Humans probably drove any remaining dinosaurs to extinction, perhaps by machismo for the honor of being a dragon slayer, or because they were pests.
Libertarian reporter John Stossel has often advocated free markets as the solution to the “tragedy of the commons,” a situation where everyone tries to get all they can from limited resources and everyone ends up losing it all. Human selfishness, he argues, can be made to work for the common good through private property rights. Individuals will protect their property; this was the lesson the pilgrims learned the hard way when coming to the New World. Once they each had their own piece of land to farm, famine turned to prosperity. Stossel and other free market economists might advocate allowing tribes to raise rhinos for profit, harvesting rhino horn and selling it. They would be the last ones to let their source of livelihood go extinct. It might be worth a try, since the situation is out of control and nothing else is working. But how is one going to control large mammals that roam over large distances? There are hard questions, and we are not taking a position on the alternatives, nor do we want to get distracted from the main point of this entry, which is the amazing system of biodiversity God created. Even as intelligent agents in a stewardship position, we are part of that biosphere, and should exercise wisdom and righteousness in our roles.