Soil conservation and restoration Flashcards
(36 cards)
What does REDD+ stand for?
Reducing Emissions from Deforestation and Forest Degradation, plus conservation, sustainable forest management, and enhancement of forest carbon stocks.
What is the main goal of REDD+?
To reduce CO₂ emissions by stopping deforestation and enhancing forest carbon sinks.
Under REDD+, how much carbon could be saved by stopping deforestation?
About 1.1 gigatons of carbon (GtC) per year.
What are the three forest-based CO₂ removal goals of REDD+ over the next 50 years?
Letting second-growth forests mature → 2 GtC/y
Restoring degraded forests → 1 GtC/y
Reforesting recently deforested land → 1 GtC/y
What is the “4 per mille initiative”?
The 4 per mille initiative is an international coalition aiming to offset the additional CO2 emissions from fossil fuels by storing an additional 4 per mille (0.4%) of carbon per year in soils. This aims to increase soil organic carbon through various land management practices.
What are some practices that can increase soil organic carbon?
Conservation tillage (maintaining soil stability) and residue management (e.g., mulch farming; directly adding C)
Applying treated organic wastes to soil (addition of C-rich material)
Using N and other nutrient sources more efficiently (supports microbes = faster C decomposition)
Converting marginal/degraded lands to restorative land uses (e.g., hedgerows).
Eliminating summer (bare) fallow and incorporating legumes (with nitrogen symbiosis) and cover crops in rotations (less erosion).
Agroforestry (growing trees alongside crops/pasture -> providing shade, hydraulic lift and stabilisation)
Why is there some reluctance to switch to better agricultural practices (in the context of increasing soil C)?
- Minimum till and cover crops have produced mixed results
- Lack of incentives (is the risk of losing crops worth it)
What are the potential benefits of restoring soil in terms of food security?
Restoring soils can enhance food security.
Adding 1 ton of soil carbon per hectare per year can increase crop yields by varying amounts depending on the crop (e.g., 20-70 kg/ha for wheat, 10-50 kg/ha for rice, 30-300 kg/ha for maize).
This could lead to a significant increase in global grain production (24-40 million metric tons)
How does the sequestration rate of C into soils change with different initial C stocks (in terms of methods to increase soil organic C)?
The lower the initial C stock the higher the sequestration rate (i.e., more C can be added because less is already present).
There is an exponential decline in sequestration rate with initial C stock.
How does the sequestration rate of C into soils change with time (in terms of methods to increase soil organic C)?
Gradual decline over time in sequestration rate - seems to reach a plateau where no more C can be added.
Globally where are the initial C stocks the highest in soils?
The land with higher C storage potential (i.e., lower initial C stocks) are below the north.
What is biochar?
Designed to be a negative emission technology and improve soil fertility.
Biochar is the product of pyrolysis of biomass (essentially charcoal – the incomplete combustion of wood).
How is biochar produced?
Through the heating of biomass in low oxygen environments. This is known as pyrolysis
How does biochar work?
Carbon captured by photosynthesis (biomass) from the atmosphere is locked into the biochar, preventing degradation and return of carbon into the air. Biochar is then applied into the soil.
This removes waste/crop residue whilst also enhancing fertility.
What is pyrolysis? What are the products?
Thermal decomposition in the absence of oxygen.
Products = gas, bio-oil and solid char
What is gasification? What are the products?
Conversion of biomass into carbon monoxide, carbon dioxide, hydrogen, methane and nitrogen with a limited supply of oxygen and/steam.
Products = syngas (mixture of gases CO, CH4, H2) and char
What is better for biochar formation - pyrolysis or gasification?
Both pyrolysis and gasification can produce biochar, but pyrolysis is the primary method because it produces a higher yield of stable, carbon-rich char.
Is biochar stable in the soil?
Biochar is very stable in soil and degraded over centuries/millennia (not as biodegradable as fresh woody biomass).
How could soils with biochar be identified from those without?
They typically appear blacker, with higher stable carbon content. Nutrient levels may or may not change depending on the type of biochar and soil conditions.
What can be added to biochar to produce the best crop growth (observed in Africa)?
Fertiliser
(Crop + fertiliser + biochar)
What are the risks of biochar?
- Can contain toxic compounds (produced during burning)
- Releases CO2 trapped in biofuel into the atmosphere (although is still carbon neutral)
What are the benefits of adding biochar to soils?
- Can bind organic compounds (e.g., pesticides) preventing leaching into water ways
- Can bind to heavy metals and persistant organic pollutants (prevents plants from taking these up)
- Can bind to nutrients, allowing a slow release to plants which is more biochar
What is bioremediation? What scenario can it be used in?
The use of either naturally occurring or deliberately introduced microorganisms to consume and break down environmental pollutants.
This can be achieved by adding lignin to soils (an aromatic compound), which biostimulates microbes capable of breaking down of polyaromatic hydrocarbons.
What is a common source of soil pollution which can be reduced via bioremediation? What is problematic about these?
Polyaromatic hydrocarbons
- Carcinogenic (toxic)
- Especially recalcitrant
