Ecosystems vs Agriculture Flashcards
Agriculture, food, and deforestation are major drivers of climate change
Land use is increasingly dedicated to pastures, arable land
Top 10 mitigation pathways for natural climate solutions
- Reforestation
- Avoided forest conversion
- Natural forest management
- Avoided peatland impacts
- Cropland nutrient management
- Trees in cropland
- Peatland restoration
- Conservation agriculture
- Reforestation of coastal wetlands
- Avoided coastal wetland impacts
The services provided to us by ecosystems in 1997 were estimated to be worth about double the value of the global economy
The essential foundations of sustainable agriculture and ecosystems and the global economy are soils
Without soil we lose almost all ecosystem services.
Soils are necessary for
Disturbance regulation, water regulations, water supply, erosion control, soil formation, nutrient cycling, waste treatment, food production and raw materials
At the heart of the module is the view that natural ecosystems are naturally self-sustaining and perpetually renewing and adapting.
We need to learn from this if we are to be effective stewards of the Earth’s resources now and for future generations.
Scientific studies of agro-ecosystems have focused on how to increase agricultural production until recently.
Sustainability has not been a major goal.
true sustainability does not deplete natural resources.
Four types of differences in our understanding of agricultural and ecosystem soil-plant relationships.
Definitions
Evaluations
Assumptions
Characteristics
Definitions:
What is soil?
Depends who you are and what you do with it
Engineer =
Drift & unconsolidated material.
Soil scientist (pedologist) =
mixture of mineral and organic compounds undergoing complex physical and chemical transformations.
Agronomist (farmer) =
depth to which cultivation takes place and the medium for crop nutrient and water supply.
Ecologist =
below-ground ecosystem which provides habitats for
plant, animal and microbial communities and controls ecosystem productivity and biogeochemical cycles.
Evaluations:
A soil which is good for agriculture is not necessarily of great ecological value.
Farmers aim to maximize profit and production.
Ecologists value diversity of flora and fauna and seek sustainability.
Virgin tropical rainforest:
Ecologist- immense value for biodiversity and C cycling.
Agronomist- no value unless timber can be sold or cleared to grow crops. People don’t eat trees.
Intensive agriculture:
Ecologist- biodiversity, ground water and soil C depleted.
Excess nutrients cause pollution. Releasing greenhouse gases.
Agronomist- Highly productive and profitable. Feeding the world human population.
Many of the ecosystem properties that farmers manipulate to enhance productivity
result in loss of diversity and ‘ecological value’ but ensure cheap food. Are intangible ecosystem values being lost?
Multifunctional agriculture accords with the recognition that environmental policy needs to take an ecosystem approach
UK agriculture generates a net positive environmental value of £650 million per year
£2.07 billion per year damages from greenhouse gas emissions
We see declining soil health in poorer productivity owing to nutrient depletion, declines in levels of humus, and erosion and compaction of soils.
There is often more biology and biodiversity belowground than aboveground. (Fungi, bacteria, arthropods and annelids)
- Drainage improves soil.
But….
Drainage releases soil C stores and normally reduces biodiversity. Large amounts of money are now being spent now trying to block drains in upland peatlands reversing poor guidance from the past!
- Only inorganic nutrients are available to plants.
But…
Some plants depend mainly on organic N and P sources in soil organic matter. Manures often provide better crop yields than chemical fertilizer.
Soil characteristics are much less diverse in agricultural rather than natural ecosystems
It has been suggested that intensification of agriculture to ‘spare’ natural ecosystems from conversion to agriculture is better than expanding less intensive agriculture into natural ecosystems.
“Land sparing” through maximizing yields off the most productive land / cropping systems may reduce the overall size of the “footprint” of agriculture but the resulting “heavy footprint” of the intense cultivation areas often involves total destruction of native habitats.
Highly intense cultivation in southern Brazil- 100% of land used for cropping every year- high inputs high outputs
Land sparing concentrates risks of major crop failures
Soil degradation reduces crop production and soil fertility- so more land needs to be converted to agriculture to compensate for this loss and more fertilizer added.
This leads to more land and water degradation and loss of ecosystem services.
UK post 1940’s agricultural intensification and productivity gains have had high ecological costs.
Whilst we notice the loss of birds and wildflowers, losses of topsoil, soil C and ecosystem engineers like earthworms & mycorrhizas go unnoticed.
UK crop yields have plateaued - and indeed fallen in recent years due to poor weather and soil constraints. This has been compounded by farmers sowing less wheat. We had to import grain in 2012.
Over 30% of maize (corn) grown in USA from 2009 is used to make bioethanol
18% fall in world grain stocks from 2000-2012
– at the same time a 14% increase in world population.
We now have less than 3 months stock globally.
“sustainable intensification” – an oxymoron?
The phrase has recently become controversial because
both its critics and some of its advocates presuppose that it refers to particular systems of production.
On the contrary, since the goal of sustainable intensification is to achieve a union between sustainability on the one hand, and productivity on the other, it is unlikely to resemble anything we have today
What are we seeking to sustain?
Basic needs- food, water, shelter, warmth etc?
Ecosystems and biodiversity?
Finite global resource conservation, reuse and recycling?
Economic sustainability?
Maintain western consumption-based lifestyles (and help others do the same)?
(NOT sustainable)
The status quo of global economic and population expansion, fossil fuel consumption and element and material exploitation? (NOT sustainable)
What is sustainable agriculture?
Producing abundant food without depleting the earth’s finite resources or polluting its environment whilst providing dependable incomes to growers.
Every calorie of food produced
requires on average 10 calories of fossil
fuel input” (Heinberg, 2008).
Globally, agriculture loses soil 10- 100 times rates of formation- soil is becoming a finite resource.
Agricultural soils have typically lost 30 to 40 t C ha-1, contributing over 20% of anthropogenic CO2 release 1850 -1990.
Nitrogen fertilizer uses large amounts of finite and polluting fossil fuel energy.
Phosphorus fertilizer uses finite rocks that are running out. Fertilizer run-off is polluting.
