Understanding the Ecology

From "Ecological Civilization", article by Fred Magdoff on Monthly Review.

Fred Magdoff (fmagdoff [at] uvm.edu) is professor emeritus of plant and soil science at the University of Vermont and adjunct professor of crop and soil science at Cornell University. His most recent book isAgriculture and Food in Crisis(co-edited with Brian Tokar, Monthly Review Press, 2010). This article is slightly revised from his presentation to the Marxism and Ecological Civilization Conference at Fudan University, Shanghai, November 17, 2010.

"Ecological Principles: Learning from Nature

The study of ecology developed as scientists began to understand how natural systems functioned. Scientists quickly realized that they needed to think and study in a multidisciplinary fashion—there was no way to comprehend the full complexity of such systems by focusing on one particular discipline or sub-discipline. 

In fact, even after intense study, it is usually impossible to understand fully a highly complex system—with interactions and positive and negative feedback loops—to the extent that you can accurately predict all the results that will occur when you intervene in some way. Frederick Engels described this phenomenon well, over a century ago in 1876:

Let us not…flatter ourselves overmuch on account of our human victories over nature. For each such victory nature takes its revenge on us. Each victory, it is true, in the first place brings about the results we expected, but in the second and third places it has quite different, unforeseen effects which only too often cancel out the first. The people who, in Mesopotamia, Greece, Asia Minor, and elsewhere, destroyed the forests to obtain cultivable land, never dreamed that by removing along with the forests the collecting centres and reservoirs of moisture they were laying the basis for the present forlorn state of those countries. When the Italians of the Alps used up the pine forests on the southern slopes, so carefully cherished on the northern slopes, they had no inkling that by doing so they were cutting at the roots of the dairy industry in their region; they had still less inkling that they were thereby depriving their mountain springs of water for the greater part of the year, and making it possible for them to pour still more furious torrents on the plains during the rainy seasons….Thus at every step we are reminded that we by no means rule over nature like a conqueror over a foreign people, like someone standing outside nature—but that we, with flesh, blood and brain, belong to nature, and exist in its midst, and that all our mastery of it consists in the fact that we have the advantage over all other creatures of being able to learn its laws and apply them correctly.1

Learning to “know and correctly apply” the “laws” of nature has progressed greatly since Engels’s time. Although we must always proceed with caution when working with complex ecosystems (as Engels warned, there may be unforeseen consequences), much has been learned about how natural systems operate, about the importance of the interactions of organisms among themselves and with their physical/chemical/climatic environment. There are fragile natural ecosystems that are easily disturbed, and may become degraded as a result of slight disturbance. However, many natural ecosystems are strong, able to resist significant perturbation and/or quickly return to normal functioning following a disturbance. Natural disturbances of an ecosystem may be sudden—a wildfire started by a lightening strike, huge winds generated by hurricanes, floods, etc.—or gradual, as with changes in long-term precipitation trends. More resilient systems are better able to adapt to long-term gradual changes as well as sudden ones.

Metabolism and Metabolic Connections

The term metabolism is usually used in reference to the work done inside an organism or a cell as it goes about its normal operations: the building up of new organic chemicals and the breaking down of others, the recovering of energy from some compounds, and the use of energy to do work. But a critical part of the metabolism of a cell or large organism is the exchange of materials with the environment and other organisms: obtaining energy-rich organic molecules and individual elements necessary to make all the stuff of life, including oxygen, carbon dioxide, nutrients (such as nitrogen, phosphorus, potassium, and calcium), and water. Without access to these resources outside itself, an organism would run out of energy and die. Plants and animals, as well as fungi and most bacteria, need to be able to obtain oxygen from the atmosphere or water in order to live. In addition, all organisms must rid themselves of waste products such as carbon dioxide that can be toxic if allowed to accumulate inside the organism. Thus, metabolism involves not only processes internal to the organism but also a continual exchange of materials between an organism and its immediate environment—the soil, air, water, and other organisms. (See Figure 1.)

Almost all organisms use the energy derived from sunlight—either producing it themselves by photosynthesis or feeding on plant material or organisms that have themselves fed on plant material. However, organisms, from the “simplest” bacteria to mammals, interact with one another and with the chemical and physical aspects of their local environment. The waste of one cell—or the whole organism itself—becomes food for another. And many organisms contain other organisms, either inside or on their surfaces, most living in a mutually beneficial, symbiotic association. The huge number of bacteria inside the human gut (as there are inside those of other animals) plays an important part in our metabolism and assists in the normal functioning of the body.

Soil is not just a medium for supporting plants so they can grow upright. It is also composed of minerals, gases (atmosphere), water, decomposing organic material, and literally millions of organisms such as fungi, bacteria, nematodes, earthworms, and so on, all continually interacting and providing resources to one another. There is a strong metabolic interaction between plants and soil. Plants, as they grow, provide food for many soil organisms, as material produced by photosynthesis in green tissue is translocated to the roots and exuded. (See Figure 1, which outlines some of the main metabolic connections in a natural ecosystem in which humans are part.)

Many of the microorganisms close to roots provide organic chemicals that support healthy plant growth. All plants also take up nutrients such as potassium, phosphorus, magnesium, calcium, and nitrogen. Some plants, such as legumes, which function symbiotically with bacteria inside the plants, supply energy-rich products of photosynthesis to the bacteria, which in turn supply the plant with available forms of nitrogen. When plants or plant roots die, they become food for fungi and bacteria that then become energy sources for organisms such as nematodes that then become food for other organisms further up a complex metabolic foodweb of life. (A foodweb is the term now used in place of food chain—because organisms are connected in complex, branching ways and not in an orderly, ladder-like chain.) Although plants make their own energy-rich compounds using the sun’s energy to power photosynthesis, the essential inorganic compounds that plants take up from the soil also participate in the foodweb. As organisms feed on dead plant material, they use energy contained in the residue for their life processes and, at the same time, convert nutrients in their food into forms that can be used by plants in the future.

Plants living in the same ecosystem are frequently connected to one another metabolically. The release of available nitrogen from a legume can, for example, be taken up by a neighboring grass plant. The threads of fungi (hyphae) that help plants take up water and nutrients frequently connect one plant to another. In addition, some plants provide resources and refuge to insects that attack insects that feed on other plants.

Plants and soils are important participants in the hydrologic cycle. Plants take up water from soil and use some for growth, while most water evaporates from leaves, returning to the atmosphere to fall back to Earth again as rainfall. Precipitation may filter into the soil and be stored there for plants to use, or it may percolate down to recharge the water table. If the soil is open and porous and has a cover of organic mulch, a high percentage of rainfall can infiltrate. Conversely, if soils are compact and have no surface organic mulch and few plants, rainfall tends to run off the land, eroding soil as it flows.

There is also an intimate and important metabolic connection between plants and higher animals, as animals feed on plants (or other animals that fed on plants), using nutrients from the soil and solar energy that have been stored in plants. In the living and reproducing processes of animals, energy is used to do work, and nutrients are returned to the soil as waste materials. There are strong animal-to-animal metabolic relationships, as carnivores, omnivores (humans included), parasitoids (insects that parasitize other insects), etc. go about their normal lives.

Humans create forms of metabolic interaction with the earth in many ways—agricultural systems, fishing, mining, production and use of industrial commodities, production and utilization of transportation systems, heating homes and cooking, disposing of solid waste (garbage), changing the landscape to accommodate road construction, etc. However, in this section, we include only human metabolic relationships with the earth as they are expressed through the consumption of food and excretion of bodily waste. This allows us to focus on what can be learned from natural systems.

Strong Natural Ecosystems

The continuity of the natural soil-plant-animal metabolic connections is critical to maintaining strong ecosystems. And within the soil, the metabolic interactions of the great diversity of organisms help provide the nutrients and stimulating compounds that are essential for growing healthy plants as well as enhancing infiltration of rainfall and storage capacity for water for later use by plants.

A number of characteristics can be thought of as pillars supporting strong natural ecosystems. These have been described as follows:

• Diversity. A great biological diversity, both aboveground and in the soil, characterizes many strong natural ecosystems in temperate and tropical regions. The metabolic connection between so many organisms provides biological synergies, nutrient availability to plants, checks on disease or insect outbreaks, etc. For example, competition for resources and specific antagonisms (such as antibiotic production by some soil bacteria) among the multitude of soil organisms usually keep soil borne plant diseases from severely damaging a natural grassland or forest. And a great diversity in species aboveground (plants and animals) and in the soil, some with overlapping niches or functions, means that if one is harmed by a disease or insect, there are frequently others that promote the continuity of ecosystem functioning.
• Efficient Natural Cycles through Closely Linked Metabolic Relationships. Efficiency of natural systems’ natural cycles is arrived at through close biological interactions and associations and biological synergies. Tight energy and nutrient flows—with little wasted or “leaking out”—are characteristic of strong natural systems. Because of the wide variety and great populations of organisms and their many natural niches in soils and on the soil surface and the presence of significant quantities of stored solar energy in crop and manure residues, energy flows efficiently, as organisms consume organic residues and one another. Natural ecosystems with healthy soils and diverse plant species also tend to be efficient in capturing and using rainfall and in mobilizing and cycling nutrients. This efficiency in use of nutrients, energy, and water helps to keep the ecosystem from “running down” through the excessive loss of energy and nutrients (and topsoil) and, at the same time, helps maintain the quality of the groundwater and surface waters. Precipitation tends to enter the porous soil, rather than run off, providing water to plants and recharging ground water, slowly releasing water to springs, streams, and rivers.
• Self-Sufficiency. A consequence of diversity and efficient natural cycles is that natural terrestrial ecosystems are self-sufficient—requiring only inputs of sunlight and rainfall. Natural ecosystems run on current and recently past solar energy (stored as soil organic matter). The sun’s energy, captured by green plants, is then used by many organisms, as fungi and bacteria decompose organic residues and are then fed upon by other organisms, which are themselves fed upon by others, higher up the foodweb.

Cycling of nutrients from soil to plant to animal and back to soil is essential for an ecosystem to be stable and resilient. There are low levels of nutrients, such as nitrates, that come along with rain and are deposited as dust settles. Other nutrients then become available as soil minerals dissolve. But, to a great extent, nutrients cycle and energy flows efficiently within the system. As organisms decompose dead plants and animals, nutrients are recycled at the same time that energy stored in the food source is utilized. The essential nutrient, nitrogen, needed for making proteins, is provided by a number of species of bacteria (free living as well as those living symbiotically on or in plant roots) that are able to convert nitrogen gas in the atmosphere into amino acids, directly usable by plants, and to release mineral forms of nitrogen that plants can also use.

• Self-Regulation. With plants and animals filling the numerous niches aboveground, many species are able to exist side-by-side, for instance, in grasslands. But they metabolically interact with one another and are intimately connected. Because of the great diversity of organisms present, outbreaks (or huge population increases) of diseases or insects that severely damage plants or animals are uncommon. For example, a particular beetle that feeds on plants may encounter numerous other species that keep its population from getting too high—“a variety of predatory bugs and beetles in the foliage of the plants, and pathogenic nematodes and fungi that inhabit the soil attack pupating adults below ground.”2

Animals have many systems to defend themselves when under attack by other organisms, including, in mammals, their own immune systems. But plants also have a number of defense mechanisms—some stimulated or induced by soil organisms—that help protect them from attack by fungi and bacteria. There are also organisms that prey on (or lay their eggs in) insects that feed on plants. Amazingly, plants being eaten by plant-feeders (herbivores) send out chemical signals that recruit the specific organism to attack the particular plant-feeders.3

• Resiliency through Self-Renewal. Disturbances occur in all ecosystems, natural or not. The stronger ecosystems are more resistant to disturbances and are able to bounce back quicker.4Such resiliency is the “bottom line” characteristic of strong and stable ecosystems, with other characteristics contributing to the ability for self-renewal. Seeds stored in the soil, which germinate after a fire are an example of the self-renewal of plants.

Are There Lessons to Learn from Bees?

The natural world contains many interesting examples that may have some analogies in human activity. For example, when beehives grow too large, bees swarm to a temporary location. Scouts go out in different directions and then report back by performing a dance that provides information about the location scouted and its conditions. Other bees congregate around the original scout they think has selected the best site. When enough bees agree on one of the locations, the entire swarm then goes off to build a hive there.5

When a large enough number of bees agree about a site, they end up selecting the best one. There is an analogous situation with humans. People in groups, provided with the necessary information, tend to make better decisions than individuals making decisions for the group. A diversity of people (backgrounds, skills, outlooks) allows a group to evaluate issues better. Because they are, as a group, involved in the decision-making process, they feel more ownership of the decision and a desire to help implement it."