ēcosystemēcology

THE ECOSYSTEM CONCEPT

ecosystem

• An ecosystem is a spatially explicit unit of Earth that includes all of the organisms, along with all components of the abiotic environment, interacting together as a system, within its boundaries.

(modified from Likens 1992)- “Basic units of nature” (Tansley 1935)- need boundaries for budgets and mass balances- can be small or large

THE ECOSYSTEM CONCEPT“UNITS OF NATURE”

SIR ARTHUR TANSLEY

The ecosystem provides a conceptual framework for the

study of the interactions among individuals, populations,

communities and their abiotic environments, and for the study

of the change in these relationships with time

from Huston et al. 1988. BioScience

“Ecosystems are, of course, systems. …A system is conceived as something that we can dissect, and recognize as made of interacting elements; something apt to change as time passes, but retaining some invariant properties. As we are free to choose these invariants, nothing escapes the definition of a system.”

Margelef, R. 1980. Towards a Theory of the Biosphere. Ed. Omeca, Barcelona. 230 pp.

ECOSYSTEM COMPONENTS

• BIOTIC AND ABIOTIC

• BOUNDARIES (SCALE)

• FLUX AND CYCLING

• CHANGE WITH TIME

• HISTORY

THE ECOSYSTEM APPROACH

THE ECOSYSTEM APPROACH1959

Various APPROACHES to the study of ecosystems

• Empirical or Natural History• Mass Balance or Budgetary• Comparative• Modeling or Computer Simulation• Long-term Studies• Experimental Manipulation (including isotopes)• Theoretical

(modified from Likens 1992)

Small watershed-ecosystem approach (Bormann and Likens 1967)

Likens 1985

Ecosystem inputs and outputs represent connections to adjacent ecosystems, and to larger, global

cycles

These connections represent the “pulse” of

the planet with regard to management

What Controls Primary Productivity in Aquatic Ecosystems?

• Phosphorus– Schindler (Science) 1977; Schindler et al.

(PNAS) 2008

• Nitrogen– Lewis and Wurtsbaugh (Internat. Rev.

Hydrobiol.) 2008

• Both (currently a raging controversy)– Conley et al. (Science) 2009, and many

others

Some Major Aquatic Problems Requiring an Ecosystem

Understanding

• Eutrophication

• Acid Rain

• Drought/flooding/climate change impacts

• Groundwater depletion

• Mining, especially Mountain Top for coal

• Toxic Algal Blooms (HABs)

• Contamination with Antimicrobials, Genetically Engineered Substances, Endocrine Disrupters, etc.

• Salinization

• Dams on flowing water

SOME PROVOCATIVE QUESTIONS FOR ECOSYSTEM SCIENTISTS TO PONDER

1. Can (should) ecosystems be modified by genetic engineering to enhance environmental quality and stability?

2. Can ecosystems be made to achieve specific functional goals (e.g. restoration)? How should the targets be set?

3. Can unexpected consequences or “surprises” be dealt with better or at least anticipated? (see, Lindenmayer et al. 2011 PNAS)

4. Can the relationship between biodiversity and ecosystem function be identified and utilized?

5. Do invasive species provide ecosystem services?

6. Should ecosystem services focus only on humans?

Ecosystem services• Ecosystem services are services provided

by functioning ecosystems for the benefit of humans and human societies (Daily et al. 1997), such as the provision of clean air, clean water, clean soil, and nourishing food. The economic value of ecosystem services has been estimated at trillions of dollars annually (Costanza et al. 1997). A limitation of the ecosystem services concept is that it is focused only on service to humans, whereas critical services must be provided to all organisms comprising an ecosystem if the ecosystem is to function properly and in a “healthy” manner.

“It is inconceivable to me that an ethical relation to land can exist without love, respect, and admiration for land, and a high regard for its value; I mean value

in the philosophical sense."  Aldo Leopold, 1949

  

“…the aggregate value of … nature[’s] – aesthetic beauty,

cultural importance and evolutionary significance – is

infinite, and thus defies incorporation into any ecosystem service programme that aims to save nature by approximating its

monetary value.”McCauley 2006 (Nature)

Ecosystem thinking

• Ecosystem thinking is the holistic approach used to analyze (think about; get your mind around) complicated problems, in which all components of the ecosystem and all known factors affecting the ecosystem are considered and evaluated. Complicated characteristics include legacies, feedback loops, cycles, circles, tipping points/thresholds, resilience, and recovery. Ecosystem thinking is a special type of systems thinking, focused, for our purposes, on natural ecosystems, including humans (see Likens and Franklin 2009. BioScience).

ECOSYSTEMS PROVIDE EXCELLENT WINDOWS FOR

OBSERVING CHANGE CAUSED BY HUMANS

Toxification ofthe biosphere

Toxification ofthe biosphere

Humans

Land-use changesLand-use changes

Global climatechange

Global climatechange

Stratosphericozone depletion

Stratosphericozone depletion

Loss of biodiversityLoss of biodiversity

Invasion ofexotic species

Invasion ofexotic species

Infectious diseaseInfectious disease

HUMAN-ACCELERATED ENVIRONMENTAL CHANGE

Updated fromLikens 1991

THE DEVELOPMENT OF THE ECOSYSTEM APPROACH AND

ITS USE IN IDENTIFYING, UNDERSTANDING AND

RESOLVING ENVIRONMENTAL PROBLEMS IS ONE OF THE

MAJOR ADVANCES IN BIOLOGY DURING THE PAST 50 YEARS

POSSIBLY NEVER BEFORE HAVE ECOSYSTEM SCIENTISTS NEEDED TO BE AS CREATIVE, INNOVATIVE, PROACTIVE AND AGGRESSIVE TO MEET THE

ENVIRONMENTAL CHALLENGES OF THE NEXT 50 YEARS