The problem of species diversity
Unlike natural ecological complexes, agroecosystems are characterized by a sharply reduced species diversity. Most often, they represent a monoculture—an area planted or inhabited predominantly by a single species of organisms.
Such uniformity has serious consequences. First, environmental resources are used extremely inefficiently. Second, contrary to popular belief, the overall biological productivity of artificial agroecosystems is generally significantly lower than that of wild, naturally formed ecosystems.
Disruption of the nutrient cycle
The main fundamental problem of any agroecosystem is the lack of a closed nutrient cycle. In the wild, biomass returns to the soil after the death of organisms, feeding new generations. In an artificial ecosystem, this cycle is interrupted by humans, who purposefully remove a significant portion of the biomass in the form of a harvest.
For the system to continue functioning, humans are forced to constantly compensate for these losses by introducing so-called energy subsidies. These include:
- Plowing of land;
- Regular watering;
- Application of mineral and organic fertilizers;
- Use of pesticides for plant protection.
To maximize yields under such conditions, specially bred plant varieties and animal breeds are used that are genetically predisposed to actively respond to such artificial subsidies.
Pests and selection features
Monoculture creates ideal conditions for parasites. The concentration of a huge number of individuals of a single species in a limited area provokes the mass reproduction of consumers and parasites that specialize in feeding precisely on this species. This leads to regular pest population outbreaks.
In addition, in agroecosystems, natural selection is completely supplanted by artificial selection. Humans cultivate exclusively those traits that are useful to them (e.g., maximum productivity, fruit size, or muscle mass), ignoring the traits necessary for the organism itself to survive.
Logical result: cultivated species possess colossal productivity in the greenhouse conditions of an agroecosystem, but their baseline survival rate is critically reduced. Finding themselves in the wild without human support and protection, they die very quickly, unable to compete with wild relatives.
Briefly: answers to topical questions
How does an agroecosystem differ from a natural biogeocenosis?
An agroecosystem differs from a natural biogeocenosis by its reduced species diversity, open nutrient cycle, and the predominance of artificial selection.
| Characteristic | Natural ecosystem | Agroecosystem |
|---|---|---|
| Species diversity | Not specified as reduced | Sharply reduced, often monoculture |
| Nutrient cycle | Closed | Open: harvest is removed by humans |
| Food webs | Not specified | Short |
| Selection | Natural | Artificial selection predominates |
| Support | Not specified | Cannot exist without human support, requires energy subsidies |
What are the causes of the low ecological stability of agroecosystems?
The low ecological stability of agroecosystems is due to their inability to exist without human support and a sharp decrease in species diversity.
Main causes of instability:
- Monoculture — the concentration of a single species leads to inefficient use of environmental resources and provokes the mass reproduction of consumers and parasites (pest population outbreaks).
- Reduced survival rate — due to the predominance of artificial selection, traits useful to humans are cultivated, which is why cultivated species quickly die in the wild.
- Dependence on anthropogenic energy — agroecosystems are rapidly destroyed by pests or displaced by wild species without the introduction of energy subsidies (fertilizers, pesticides, irrigation).
What environmental consequences are caused by the excessive use of fertilizers and pesticides in agroecosystems?
The excessive use of agricultural fertilizers and pesticides is associated with environmental chemical pollution.
Main environmental consequences:
- Water and soil pollution — fertilizers and pesticides enter the environment as chemical pollutants.
- Hydrosphere pollution — drainage water from irrigated lands is a source of hydrosphere pollution; pesticides and mineral fertilizers can contaminate water bodies and seafood with toxic substances.
- Deterioration of food quality — food products can be contaminated with residual amounts of pesticides and nitrates.
- Need for sanitary protection of soil — soil must be protected from chemical pollution, including pesticides and agricultural fertilizers.
The differences of an agroecosystem are easy to remember by the three "M"s: Monoculture (one species), Minus cycle (humans take the harvest), Modification of selection (artificial instead of natural).
Class and exam questions
What will happen to a cultivated plant variety in the wild?
It will die quickly. Artificial selection develops traits in organisms that are useful for humans (high yield), but at the same time critically reduces the overall survival rate of the species outside the artificial environment.
Why are energy subsidies needed in agriculture?
Since humans remove the harvest, the natural nutrient cycle is interrupted. Subsidies (fertilizers, irrigation, plowing) are necessary to replenish the removed resources and maintain the life of specially bred varieties.
Why do pest invasions often occur in fields?
The reason lies in the cultivation of a monoculture. A huge concentration of individuals of only one species creates an unlimited food supply for those consumers and parasites that feed on them, provoking their mass reproduction.
What else to study on this topic
- Mechanisms of pest population outbreak formation in monocultures
- Types of energy subsidies and their impact on productivity
- Comparison of productivity between climax communities and agroecosystems
- Impact of artificial selection on the viability of cultivated species
- Ways to optimize the use of environmental resources in agriculture
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