Themes

Earth as a System

A system is any set of objects or attributes which have a coherent relationship with each other (exchanges of energy and/or matter) and are bounded from the external environment or other systems. This general definition applies at any scale and in the environment it is not uncommon to be able to idenfity hierarchies of systems

isolated systems-no exchanges of energy or matter beyond the bounds of the system. Relative uncommon in the environment

closed systems--Open to exchanges of energy but not matter which must be stored within the system and recycled. The earth/atmosphere system is a good example

open systems--open to exchanges of energy and matter. Typical of most systems within the overall earth/atmosphere system. Human body, a pond, prairie, forest, etc would be good examples of open systems

Energy from the sun (electromagnetic radiation) is the primary input to the earth/atmosphere system.

This energy is either absorbed or reflected from the earth/atmosphere system and stored or transmitted from one system to another and eventually emited back into space

As a result of these transformations this energy drives almost all processes found on the surface and is responsible for all change. This includes fossil fuels, the human body, weather, plant growth and the breakdown and re-establishment of various chemical compounds.

Other sources of energy come from the interior of the earth and include earthquakes, volcanism and mountain building and which are generally limited in location and intensity

Ecosystems

ecosystem--a system of dynamic interpendent relationships with both abiotic and biotic components; i.e. more than just plants and animals

-biotic components include plants animals, fungi, bacteria, etc

-abiotic components include climate , soils (which has biotic components), rocks and landforms and water.

-stable ecosystems exhibit inputs outputs and storage of energy and matter

-biotic components live in balance

-imbalances may result in rapid change and or decay of system

-removal of one key member of a given trophic level such as predators of a deer population

-ecosystems have the ability of process wastes(natural and manmade) but can be overwhelmed

-works like the human body in this way

Man's role in Ecosystem Functioning

The role of man on the planet has been one of modification of natural systems so as to manipulate or in some cases totally alter the existing physical landscape in order to accomplish one of the following:

-provide material for shelter i.e. cutting down forests

-provide space for ordinary living activities i.e. altering prairies so as to provide home sites, roads, shopping centers and the like

-obtain food by means of crop agriculture

-almost total elimination of existing ecosystems and replacement with monoculture with resulting concentrations of pesticides, nutrients, etc

-addition or removal of some ecosystem components for various purposes

-removal of water from streams and ground for irrigation results in water table decline and drying up of streams

-almost total obliteration of long term functioning ecosystems for a one time extraction of a specific resource

-strip mining of coal

-cutting of tropical rain forests for specific timber types while eliminating hundreds of other potentially valuable species

many ecosystems are altered inadvertently by means of introduction of exotic species or allowing for non native invader species to thrive (e.g. many grasses in Nebraska)

What do we mean by environmental health?

Text definition on page 7 "Environmental health comprises those aspects of human health, including quality of life, that are determined by physical, biological, social and psychosocial factors in the environment. It also refers to the theory and practice of assessing, correcting, controlling and preventing those factors in the environment that can potentially affect adversely the health of present and future generations"

I would like you to consider a slightly different definition in that we might look at environmental health in such a way to consider a healthy environment from the environmental perspective in that a healthy environment represents an environment in which the ordinary environmental processes involving exchanges and storage of energy and matter (to include biogeochemical cycling) are allowed to operate at a near optimal level given available substrate (rocks), landforms and climate conditions. This does not mean that human activities can't have an impact on such an environment, only that they operate in such a way as not to interfere with the operation of various functions on long term time scale.

Keep in mind that this functioning may be destroyed by totally "natural" processes such as a volcanic eruption but the environment is naturally capable of adjusting in such a way as to re-establish the various processes that existed before

Many alterations we make to the environment have long term implications which we may or may not completely understand. Some examples follow:

-introduction of chlorofluorocarbons and the resultant destruction of ozone

-paving over an area with concrete may elmost totally eliminate most biological activity for hundreds if not thousands of years

-soil erosion in the local area has removed productive topsoil at a rate that might take as long as a thousand years or more to replace

-nuclear waste disposal?

Ecosystem Health

An ecological system is healthy and free from "distress syndrome" if it is stable and sustainable--that is, if it is active and maintains its organization and autonomy over time and is resilient to stress--from Costanza et al, 1992

How do we measure ecosystem health?

Very difficult to accomplish in that it requires a thorough knowledge of most elements of the system and how they relate to each other as well as keeping track of flows of storage of energy, water and various nutrients that are an integral part of the system. Almost always involves subjective judgements

Usually involves evaluation or measurement of certain elements which we believe are indicators of ecosystem health and not looking at the ecosystem as a whole

What is the relationship between ecosystem health and human health?

A healthy functioning ecosystem may not necessarily be advantageous to the needs and wants of humans in their current population numbers.

-a prairie ecosystem provides few plants directly for human consumption and may support fewer grazing animals than a system composed of commercial grazing farms and feedlots

-the Sandhills is not very productive in the sense of producing food for human consumption but can be an extremely healthy functioning ecosystem

Some naturally functioning ecosystems may have elements that are extremely "unhealthy" from the human perspective.

-a malaria infested tropical swamp

-a tropical savanna with large carnivores

-an arctic tundra in winter

Some diseases which relate to environmental factors are exascerbated by poor choices and habits of people both groups and individuals and may be indirectly caused by human action

-e.g. lack of care in food preparation, washing hands, etc

-lack of basic air pollution control measures such as scrubbers on smokestacks, catalytic converters on cars, use of proper gasoline, etc

 

Environmental Health from a human perspective.

WHO-1992" Health is only possible where resources are available to meet human needs and where the living and working environment is protected from life threatening and health-threatening pollutants, pathogens and physical hazards.

Many human health problems are the result of an unhealthy or improperly functioning environment but even a healthy environment or ecosystem may have elements that impact human health

a naturally arid environment with substantial dust particles in the air may cause respiratory problems

Any environment produces a set of physical conditions which humans must deal with in some fashion either through adapting in some fashion to the conditions, ignoring them or more likely altering the environment in such a way as to supposely remove the problem

Pollution, including air, water and soil has many natural causes, but most come about as a result of