What is an ecosystem?
An ecosystem is a biological community of interacting organisms and their physical environment.
What is a managed ecosytem?
a managed ecosystem describes a dynamic association of plants, animals, soil, atmosphere influenced by human decision-making.
- -> AKA an ecosystem but controlled by human decision-making more than random events.
- -> Changing structure and composition for our benefit: to create surplus for food, etc
What is ecological sustainability in managed ecosystems?
“…. agricultural fertility is the survival of natural process within the human order.”
- Wendell Berry
How to retain natural process in the human order?
Through considering systems in terms of nested scales, at each of which different criteria and objectives apply.
e.g. in natural:
bioregion => catchment => ecosystem => patch
e.g. in agricultural managed ecosystem:
state => catchment => farm => paddock
What are Wendell Berry’s natural processes?
IN 3 BROAD CATEGORIES:
- Flow of energy (renewable + non-renewable, inc. solar of sun)
- Cycling of materials (water + nutrients)
- Flow of information (genes + memes)
What’s a meme?
According to R. Dawkins evolutionary biologist: meme: a unit of cultural inheritance, anything you pick up from your culture and pass on.
What’s a trophic level?
A way of viewing systems in terms of the flow of energy between organisms.
- > Helps describe function rather than simply composition and structure.
- -> Important because usually we just fall back to ‘counting things’ (composition) bc its easier, but less effective for conservation.
What is biodiversity?
Biodiversity considers composition, structure, and roles/functions of populations.
–> Requires an understanding of trophic levels, energy flows and their role in trophic hierarchies + food chain is vital to understanding how to protect different species in the name of biodiversity: normally we only focus on composition + structure bc easier to count than understand complex behavior.
What is an ag system?
Ag is a simplified, synthetic, short-lived imitation of natural ecosystems.
What are some disruptions to the water cycle?
- Replacing trees + shrubs with annual short-root crops
- Tapping into aquifers
- Salinity
- Drying out flood plains
- changing evapotranspiration (reduced)
- Changing where in the landscape water sits + for how long
- less vegetation means water can move faster down a slope and sit for longer leading to waterlogging.
- less uptake and evapotranspiration by plants means more extreme fluctuations in drought and flooding.
thus, total mass of water is same but concentrated in different part of landscape, to its detriment.
What are some of the disruptions to the carbon cycle?
- large injection of GHGs and global warming
- reduced organic matter in soil: need more soil C storage
- dependence on fossil fuels
example of amount same, but changed in form and location.
What are some of the disruptions to the nitrogen cycle?
- Haber process: at hundreds of degrees and high pressure what bacteria have done at ambient pressure and temp since forever. Allows to feed billions.
- eutrophication + energy use
- case study: excess nitrogen in dairy farms: 60-100kg of excess left on farm that doesn’t go out as outputs, some volatilizes, some leeches into soil and waterways, increasing 60 to 100 over a few decades. Because terms of trade are constantly declining for farmers.
What are some of the disruptions to the nitrogen cycle?
- initially very unavailable in soil: many cool plant adaptations to extract it out, but now we have tonnes.
- Similar situation to nitrogen.
What does natural resource management need to have an impact?
Natural resource management needs to be…
- Institutionally acceptable
- Socially acceptable
- Biologically feasible
- Economically viable
