Ecosystem Dynamics: Population and Human Impact
Ecosystem Population Dynamics
A population is a group of individuals of the same species that interact within a specific space. Demographic parameters, such as size, age distribution, birth rate, and mortality rate, are used to characterize it.
Population growth is conditioned by the availability of environmental resources and interactions with other populations in the community.
- Environmental resistance refers to all biotic and abiotic factors that limit population growth.
Population Growth Curves
In an ideal ecosystem with unlimited resources, a population would grow exponentially. This growth, plotted against time, results in a J-shaped curve.
Exponential growth occurs under special conditions and cannot be sustained for long in nature. Eventually, resources become depleted, leading to massive mortality.
Under natural conditions, in an environment with limited resources, a population initially grows exponentially. However, environmental resistance slows this growth. The population then grows slowly and stabilizes around a certain value. This growth pattern results in an S-shaped curve.
The value around which the number of individuals in a population stabilizes is called the carrying capacity (K) of the ecosystem. This value indicates the maximum population size that can be maintained more or less stably without causing environmental degradation. Populations fluctuate around K, and the population growth is considered to be stationary or in equilibrium.
Reproductive Strategies
Species can exhibit two different reproductive strategies based on their population growth patterns:
- r-strategists: These are opportunistic or pioneer species inhabiting unstable ecosystems in their early stages of development. They have a relatively short lifespan and a high reproduction rate, producing a large number of offspring. Many small organisms, such as bacteria, algae, many insects, and herbs, fall into this group.
- K-strategists: These are specialist species adapted to living in stable environments. Individuals are long-lived, and most reach adulthood. Although they may reproduce several times in their lives, their reproduction rate is low, and they have few offspring. Most birds and mammals belong to this group.
Human Impact on Ecosystems
Over millions of years, changes in ecosystems were primarily natural. Today, the human species is responsible for most of the changes occurring in ecosystems, and these changes are happening at an accelerated pace.
The world population is growing exponentially, resembling a population in an ideal ecosystem with *un*limited resources. Maintaining such a large population requires significant resource consumption, including space, food, raw materials, and energy. This also generates a large amount of waste.
Natural Resources
A natural resource is anything that people take from nature for their benefit and to satisfy their needs.
Humans only use a portion of available resources. The reserve is the amount of a natural resource that can be exploited in an economically viable way.
Natural resources are classified based on their availability:
- Renewable resources: These can regenerate over time.
- Non-renewable resources: These do not regenerate, at least on a human timescale, and reserves tend to decrease as they are consumed.
Threats to Biodiversity
Humans are part of ecosystems and depend on other living things to maintain balance.
Certain human activities threaten biodiversity:
- Overexploitation (e.g., overfishing).
- Habitat destruction (e.g., due to pollution).
- Introduction of invasive species.