The Impact of Plants and Animals on the Landscape

The Impact of Plants and Animals on the Landscape

• Biosphere boundaries are tough to pin down because the biosphere impinges spatially on the atmosphere, lithosphere, and hydrosphere.
• Both plants and animals interact with other components of the natural landscape and may be important influences on the development and evolution of soil, landforms, water, and more.
• Consists of all organisms that live on Earth.
• Vegetation used to cover most of the land surface, but no more because of humans.
• Humans have altered and modified much of the remaining vegetation in the world.

The Geographic Approach to the Study of Organisms

Because of the complexity of organisms, geographers can only focus on certain aspects rather than the whole.

Seek generalizations and patterns (in distributions and relationships) and assess their overall significance.

• Biogeography—the study of the distribution patterns of plants and animals, and how these patterns change over time.
• Biodiversity—refers to the number of different kinds of organisms present in a location.

Flora and fauna

There exist approximately 600,000 species of plants and 1.2 million species of animals.

• Biota—total complex of plant and animal life
• Flora—plants
• Fauna—animals
• Oceanic biota—living in the oceans
• Terrestrial biota—living on land

Animals in oceans divided into:

• Plankton—floating plants and animals
• Nekton—fish and marine mammals that swim freely
• Benthos—animals and plants that live in or on the bottom

The Search for a Meaningful Classification Scheme

• Systematic study of plants and animals is the domain of biologists.
• Linnaean system—most significant and widely used biological classification.
• Focuses on the morphology of the organisms and groups them on the basis of structural similarity.
• Principal disadvantage for geographic use is that it is based entirely on anatomic similarities.
• Geographers are more interested in distribution patterns and habitat preferences.
• Can’t come up with anything better.
• Widespread agreement on a scheme is very unlikely.

Ecosystems and Biomes

• Ecosystem—all of the organisms in an area and their interactions with the immediate environment
• Biomes—large recognizable assemblages of plants and animals living in a functional relationship with the environment.

Biogeochemical Cycles

Believed that for the past billion years or so, the composition of Earth’s atmosphere and hydrosphere had been relatively unchanged.

Grand cycles have kept everything in a steady-state condition:

• Flow of energy through photosynthesis
• Hydrologic cycle
• Carbon cycle
• Oxygen cycle
• Nitrogen cycle
• Other mineral cycles

Human impact is having a deleterious effect on every one of these cycles.

The Flow of Energy

Solar energy—the basic source of energy, and is fundamental for life on Earth.

Photosynthesis—the basic process whereby plants produce stored chemical energy from water and carbon dioxide and which is activated by sunlight.

How solar energy ignites life processes in biosphere:

Solar energy becomes fixed in the biosphere via photosynthesis by green plants.

In the presence of sunlight, green plants take carbon dioxide from air, combine it with water, and create carbohydrate compounds, a form of chemical energy.

This chemical energy then flows through the biosphere when animals eat the plants or eat other animals that had eaten plants.

Two main components are the hydrogen cycle and carbon cycle.

CO₂ + H₂O (via sunlight) → carbohydrates + O₂

Plant Respiration—the consumption by plants of stored energy in the form of carbohydrates.

The stored energy is oxidized by the plant, releasing water, carbon dioxide, and heat energy.

Carbohydrates + O₂ → CO₂ + H₂O + energy (heat)

Net Primary Productivity

• Net photosynthesis—the difference between the amount of carbohydrates produced in plant photosynthesis and lost via plant respiration.
• Net primary productivity—the amount of net photosynthesis of a plant community over a period of a year, or a measure of the biomass of that community.
• Net primary productivity varies geographically, with the greatest productivity in the tropics and decreasing amounts toward the poles.

The Hydrologic Cycle

Also called water cycle; imperative to life.

Water is found either in residence or in transit.

The Carbon Cycle

Carbon cycle—the change from carbon dioxide to living matter and back to carbon dioxide.

Atmospheric carbon dioxide is photosynthesized into carbohydrate compounds.

Some of the carbon dioxide is consumed directly by plant respiration.

Plant growth is dependent on a surplus of carbohydrate production.

Humans have interfered with the delicate balance in the carbon cycle that had been fixed by photosynthesis.

Through the burning of fossil fuels, humans are rapidly accelerating the rate at which carbon is freed from reservoirs and converted into carbon dioxide.

The Oxygen Cycle

Oxygen cycle—the movement of oxygen through the environment by various processes.

An extremely complicated process because oxygen occurs in many chemical forms and is released into the atmosphere in a variety of ways.

Oxygen now in the atmosphere is largely a by-product of vegetable life.

The Nitrogen Cycle

Nitrogen cycle—an endless series of processes in which nitrogen moves through the environment.

Nitrogen comprises 78 percent of the atmosphere, but only certain species of soil bacteria and blue-green algae can use it in this gaseous form; need the nitrogen cycle so other life forms can assimilate nitrogen.

Nitrogen fixation—conversion of gaseous nitrogen into forms that can be used by plant life.

Denitrification—conversion of nitrates into free nitrogen in the air.

Humans are significantly altering the balance of the natural nitrogen cycle through agriculture processes and crop choices.

Affecting lakes and streams by depleting their oxygen supply.

Mineral Cycles

Specific trace minerals—notably phosphorus, sulfur, and calcium; play important roles as nutrients for life.

Like carbon, oxygen, and nitrogen, they move over and over through cycles.

Cycles are variable from place to place.

The amounts of biotic nutrients are finite.

Human interference is either damaging or modifying some of these cycles. 

Food Chains – sequential predation in which organisms feed upon one another, with organisms at one level providing food for organisms at the next level, and so on. Energy is thus transferred through the ecosystem.

The term chain is misleading because there is not an orderly linkage of equivalent units, as a chain implies.

Fundamental unit in any food chain are the producers (autotrophs), or plants.

They trap solar energy through photosynthesis.

Followed by primary consumers and secondary consumers.

Several levels of secondary consumers.

Decomposers serve as a critical player in returning nutrients back to the soil.

Food Pyramids—another conceptualization of energy transfer through the ecosystem from large numbers of “lower” forms of life through succeedingly smaller numbers of “higher” forms, as the organisms at one level are eaten by the organisms at the next higher level.

Pollutants in the Food Chain

Increasing concern that some chemical pollutants can become concentrated in food chains.

Some stable substances (those resistant to degradation), such as DDT, and heavy metals, such as mercury and lead, become concentrated at higher levels of a food chain.

These can result in harmful effects and even the death of consumers at the top of the food chain.

Biological Factors and Natural Distributions

Questions regarding the distribution of organisms:

• What is the range of a certain species or group of plants/animals?
• What are the reasons behind this distribution pattern?
• What is the significance of the distribution?

Evolutionary Development

• Darwinian theory of natural selection explains the origin of species via descent, with modification, from parent forms.
• Progeny best adapted for a particular environment will survive.
• To understand the distribution of any species, we must first consider where it evolved.

Migration and Dispersal

• Most plants and animals possess active mechanisms to disperse themselves or their progeny.
• The contemporary distribution pattern of many organisms is often a result of dispersal from an original center.

Reproductive Success

Reproductive success is critical for the survival of a species.

Poor reproductive success can be a result of several factors:

• Heavy predation
• Climatic change
• Failure of food supply
• Changing environmental conditions can also favor one group over another.

Population Die-off and Extinction –Species’ range can be diminished by the dying out of some or all of it.

Plant Succession—when one type of vegetation is replaced naturally by another.

Usually a sequence of a lake to a field to grasses and shrubs to forest vegetation.

Extinction is permanent, but species succession is not.

Environmental Factors

A generalization that is true on one scale may be invalid on another.

Whatever the scale, there are nearly always exceptions to the generalizations.

The smaller the scale, the more numerous the exceptions.

Small scale shows a relatively large portion of Earth’s surface.

In environmental relationships, two types of competition are at work:

Intraspecific competition—among members of the same species.

Interspecific competition—among members of different species.

Limiting Factor—the most important variable determining the survival of an organism.

The Influence of Climate

• Various climatic factors exert the most prominent environmental constraints:
• Light
• Moisture
• Temperature
• Wind

Photoperiodism—the response of an organism to the duration of exposure to light in a 24-hour period.

Availability of moisture governs broad distribution patterns of the biota more significantly than any other climatic feature.

Wind is not as influential as other climatic factors, except where winds are persistent.

Influences temperature and moisture.

Edaphic factor—soil characteristics.

Influence biotic distributions:

Directly affecting flora.

Usually indirectly affecting fauna.

Topographic Influences

On global scale, topographic influences are the most important factor affecting distribution.

Wildfire

Wildfire is the most important of the abrupt and catastrophic events that affect the distribution of plants and animals.

Has a widespread influence, affecting all portions of the continents except for always-wet regions and always-dry regions where there is not enough combustible vegetation.

Environmental Correlations

Climate influences vegetation distributions more than any other environmental factor.

Also influences faunal distribution, but not as much as vegetation patterns do.

Energy for the Twenty-first Century: Biofuels

To reduce greenhouse emissions from burning fossil fuels, alternative energy sources have increasingly been investigated.

Ethanol, an alcohol fuel, and biodiesel, created from chemically processed vegetable oil and animal fat, are two that have been considered.

While the burning of both ethanol and biodiesel generate CO₂, they are burning “new carbon,” and the CO₂ emissions they contribute to the atmosphere can be readily extracted from the atmosphere by plant and animal growth.

By contrast, fossil fuels such as coal and oil utilize carbon that has been locked away for millions of years and create CO₂ emissions that cannot be readily removed from the atmosphere.

Because of their potential to reduce carbon emissions, biofuel production was mandated by the U.S. government in 2007.

There are problems with biofuels as an alternative energy source.

Corn ethanol, as well as many other forms of biofuel, takes more energy to produce than they provide.

Currently about one-third of the corn grown in the United States goes into making ethanol.

Sugarcane ethanol possesses a positive energy balance, but Brazil (the leading producer of sugarcane ethanol) has replaced tropical forests at the cost of planting more sugarcane for energy production.

In cap-and-trade energy agreements, biofuels are considered carbon neutral.

However, the effects of land-use change and energy used in production are not taken into account.

There is also an ethical issue regarding the use of arable land to produce biofuels as opposed to edible crops.

Biofuels are contributing to world hunger and increasing food prices.

Food prices in the United States have increased 10–20 percent.

Scientists are now turning to other biologically-produced energy such as yeast, algae, and bacteria.

Global Environmental Change: Honey Bees at Risk

Honey bees (Apis mellifera) are important pollinators of about one-third of the world’s crops.

Beeswax, produced from honeycomb, is used in foods, cosmetics, and pharmaceuticals.

Threats to the honey bee represent a threat to the global economy.

Colony collapse disorder, or a dead colony, is caused by a variety of pathogens, particularly in combination with each other.

The Varroa mite is a parasite of honey bee colonies that has become a common threat since the 1980s.

Affect honey bees directly by reducing their life-span through feeding on their circulator system fluid.

Affect honey bees indirectly by serving as “vectors” that can spread up to 20 viruses.

Left untreated, an infested colony will likely die in 1–3 years.

Dispersal of the Varroa Mite

Similar to other dispersal patterns, such as those used on invasive plant species along the U.S. interstate highways.

In the early twentieth century, the mite was only found on the island of Java.

By the second half of the twentieth century it was found worldwide.

One theory as to the mite’s prolific dispersal is related to the spread of improvements in transportation after World War II, associated with both natural and commercial shipment of honey bees.

As of 2014, Australia remained free of the parasite.

Future Impacts on Bees?

The removal of an entire species could have long-range and unforeseen consequences on all levels.

Researchers are studying certain honey bees that defend themselves through grooming behaviors that brush off the mites or bite off their legs.

If genes responsible for these defensive measures can be isolated, scientists can selectively breed honey bees that display those behaviors.