10/23/2008
Eckart II: Biosphere 1 – The Life Support System of the
Earth
(Fundamentals of Ecology and Spacecraft Scaling
Considerations)
Learning Objectives
Terrestrial
Environment
Geology
Provides necessary elements and infrastructure for life support and habitation, geothermal energy
Atmosphere
21% O2, 350-380 ppm CO2, exponential decay of total pressure, wind (cooling/heating and energy)
Gravity
Many g-dependent physical and physiological processes
Magnetic Field
Protects Earth from ionizing radiation
Makes compasses work, navigation
Sun
Solar energy, light
Ecology – “the study of the house”
Ecology is the scientific study of the interactions that determine the distribution and abundance of organisms.
Fauna (animals) and flora (plants and bacteria)
Study of ecology can be approached from 3 points of view:
Descriptive – natural history proceeding from descriptions of vegetation groups (temperate deciduous forests, tropical rain forests, grasslands, tundra), along with the animals and plants and their interrelationships with each of these ecosystems
Functional – oriented more towards relationships and seeks to identify and analyze populations and communities as they exist and can be measured now
Evolutionary – study of the ultimate causes of particular adaptations
Descriptive ecologists characterize the existing system
Functional ecologists ask ‘how’ the system operates
Evolutionary ecologists ask ‘why’ it is the way it is
All 3 have shortcomings…
Descriptive approach can get bogged down in endless details
Functional approach can lose touch with reality in absence of detailed biological knowledge
Evolutionary approach can degenerate into undisciplined speculation with untestable hypotheses
Central problem of economically oriented fields such as forestry, agriculture, fisheries and wildlife management is how to produce the greatest crop without endangering the resource being harvested
Maximum sustained yield – basis of resource management since the 1930’s
Based on mass: births + growth = natural loss (mortality) + harvested yield
Maximum yield is obtained from populations maintained at less than maximum density (mid-log on the sigmoid curve theory (p. 384, Krebs)
Simple logistic models combine these factors into one variable – population – with ecological assumptions that no time lags operate in the system and age structure has no effect on population (useful for populations in steady state that do not change greatly from year to year)
Habitat, interrelations with other organisms (competition or predation), temperature, moisture, other physical and chemical parameters (soil, nutrients, light, pH, salinity, oxygen, fire, etc.)
To harvest a population in an optimal way, we must understand the factors that regulate abundance. As humans so frequently mismanage exploited populations is partly a measure of ignorance of population dynamics. Management of forestry, fishery and wildlife resources is at present based more on rules of thumb and empirical results than scientific knowledge and accurate forecasting abilities. This makes design of a Closed Ecological Life Support System (CELSS) challenging, to say the least.
ECLSS
Environmental Control and Life Support System
Physical / Chemical-based
CELSS or BLSS
Closed / Controlled / Contained Ecological Life Support System
Biological Life Support Systems
Levels of hierarchical ecological integration
Biosphere – meteorology, geology and geochemistry…
Biome / Biogeographic Region – large regional units / major continents and oceans
*Ecosystems – ecological community together with its abiotic (non-living) environment
*Communities – species diversity, biotic
*Populations – density
Organisms
Organ systems
Organs
Tissues
Cells
Subcellular organelles
Molecules
* = primary levels pertaining to ecology
Consider the division between:
developed or fabricated (cities, industrial parks and transportation corridors – fuel powered systems)
cultivated or domesticated (managed agriculture, lakes and ponds – subsidized solar powered, human controlled systems)
natural landscapes (self-maintained systems)
S/C LSS can be thought of as “developed” (P/C) or “cultivated” (BLSS) systems
Consider how the Earth currently provides our LSS and whether or not the processes are “natural” or human assisted
Food production, water recycling, waste assimilation and processing, air purification, etc.
Properties state variables
Forces energy, causal drivers (heat, light, chemical, osmosis, biological, gravity?)
Flow paths connectivity between subsystems
Interactions modify, amplify or control
Feedback loops upstream influence
NASA Modeling
Projects
Advanced Life Support Sizing Analysis Tool (ALSSAT)
Systems Integration, Modeling and Analysis (SIMA)
EVA Systems Sizing Analysis Tool (EVASSAT)
Primary functional categories
Energy Source – solar, combines with abiotic materials
Heat Sink – energy byproduct
Producer – converts and concentrates solar energy
Consumer – uses converted energy and produces abiotic waste
Storage – buffer
Interaction – process resulting in higher (more complex) energy state
Redundancy in the biotic community contributes to resilience of the ecosystem
It is much safer to have more than one kind of organism (system) carry out a vital function
Advantages – renewability and high ‘quantity’
Disadvantages – low ‘quality’
Sun + plants + time/fossilization = coal (1000’s x energy concentration than solar)
Electricity is 8,000x more concentrated than solar energy
Or in terms of the food chain – sun – plants – herbivores – predators
Exchange of chemicals between abiotic and biotic components of the biosphere (illustrated on page 29 of the text)
“Uphill” cycle driven by the sun (evaporation) – represents ~1/3 of total incident solar energy
“Downhill” cycle – rain
Denitrification – puts nitrogen into the air
Nitrification (biofixation or nitrogen fixation) converts gaseous nitrogen into ammonia, nitrite and nitrate, which are usable by autotrophs (An organism capable of synthesizing its own food from inorganic substances, using light or chemical energy. Green plants, algae, and certain bacteria are autotrophs.
Green plants, algae, and certain bacteria are autotrophs - organisms capable of synthesizing their own food from inorganic substances, using light or chemical energy
Legumes (peas and beans) and certain other plants (clover) form symbiotic relationships with nitrogen-fixing bacteria (rhizobium) that live in nodules on their roots to procure nitrogen from the atmosphere – “self-fertilizing”
CO2 is mainly distributed in atmosphere, oceans, terrestrial biomass and soils/fossil fuels
Atmospheric pool is small, but dynamic compared to other compartments
CO2 is primary gaseous form, but also exists in CO and CH4
In Biosphere 2, many things happened that affected the C cycle, the net result of which was low food production and low oxygen, without a serious CO2 problem. Formation of calcium carbonate in the internal concrete structure of the Biosphere prevented excessive CO2 accumulation in the atmosphere. The otherwise high CO2 partial pressure was in part the result of microbial metabolism of excessive starting levels of labile carbon in the soil.
Phosphorous Cycle
Phosphorous required for energy transformation distinguishing living protoplasm and nonliving material, and is “hoarded” by living organisms
Element is important in plant and animal physiology and is a
constituent of all animal bones, in the form of calcium phosphate
Requires energy of some source – biological, solar or fuel
Detritus consumers, microbes and animals – natural recycling
Fuel energy used to recycle water, fertilizers, metals, paper, etc.
Liebig’s law of the minimum – overall growth is limited by least available nutrient (mainly applicable to steady state conditions)
Least applicable under transients state conditions with unbalanced flows and rates likely to depend on rapidly changing concentrations based on interactions of many factors.
CELSS Design Challenges – transients resultant from small buffer size, g-dependent responses, variations in CR, and many other potential factors
Earth’s endangered ‘life’ support system – global warming, floods, drought? (For humans maybe, but life? nah…)
Gaia Hypothesis (Lovelock)
“The biosphere is a self-regulating entity with the capacity to keep our planet healthy by controlling the physical and chemical environment.”
A spacecraft’s life support system has the same goal…