Lecture 1: Why study plants? Global carbon cycle. Food security. Flashcards
Why study plants?
• Over 90% of Earth’s biomass
• Photosynthesis sustains terrestrial and aquatic ecosystems
• Provide food for an ever‐expanding world population
• Provide energy (biofuels), housing, clothing, pharmaceuticals and
recreation
plants have 3 remarkable features:
- physiology
- biochemistry
- development
remarkable physiology:
Lack of organismal homeostasis means each cell
has to cope with environmental stresses (temperature, water, nutrients, light
etc).
remarkable biochemistry:
Each cell is multi‐functional, simultaneously like
many animal organs. Plants are good at defence (pathogens, herbivory:
secondary metabolites, hence pharmaceuticals).
remarkable development:
Development highly influenced by
environmental factors. Development and control of gene expression are
unique.
The global carbon cycle:
- Rate of CO2 assimilation and release (respiration & decomposition) are matched
- but rate or release of carbon from fossil fuels (coal, oil gas) is not matched by the rate of sequestration into deep oceans. hence build up in atmosphere
is photosynthesis a big process?
• Annual energy use is only ~10% of net primary production
• Total stored fossil carbon only ~70 years of net primary production
• One hour of sunlight falling on our planet is equal to all the energy we use
globally in a year.
anthropogenic
originating in human activity.
anthropogenic changes in CO2–>
changes in land use = clearing of forests & the cultivation of soils for food or biofuel production
AND combustion of fossil fuels.
BOTH INCREASE CO2
atmospheric CO2 concnetrations at mauna loa (PPM)
1960 just below 320 ppm
in dec 2016 = 404 ppm. v quick increase
patterns of CO2 conc at Mauna Loa due to
decreases in summer, increases in winter. WHY?
most vegetation in northern hemisphere. in summer much more carbon fixation
CO2 and O2 conc ove rlast 3500 million years
CO2 has reduced from 50,000
O2 has increased to 21%
has been fluctuations in both. Due to rubsico, O2 - evolving photosynthesis and land plants
how can you date O2 -evolving photosynthesis
2-2.5 billion years ago
Stromatolites - cyanobactierum found
BIFs : iron –> oxidised, precipitate out. Date shows oxygen increase
in 2010-2012 how many were suffering from chronic undernourishment
870 million / 7.1 billion people in the world (1 in 8) - almost all in developing countries
production of food must increase by at least 50% by
2050 even to maintain status quo
complications with increasing food production
• Less land : Arable land area 3.9% of the Earth’s surface area. Land for agriculture is declining (urbanisation). • Less water: Water resources declining, currently 1% of global water • Fewer inputs: Some nutrient resources are largely non‐renewable (P), costs of fuel and fertilisers (N) are increasing • Increased dietary demand for animal protein (from feed grain) • Increased demand for biofuels • Less labour (urbanisation) • Climate change • Weak technology and infrastructure of developing countries
form 1960 - 2000 3 main crops: comment on production & price DUE TO
Production increased rapidly
price decreased.
because of green revolution - creation of genetically improved crop varieties (by breeding), & improved agronomic practices. more food & cheaper food
food security requires a
Second Green Revolution.
A 50% increase in crop yields in 40 years requires a
compound rate of increase of ~1% per annum
The green revolution: is there any evidence that we’ll reach the 50% increase by 2050?
NO.
Average yield beginning to plateau.
Avergae yearly increase over previous 10 yrs - increased now decreasing again (upside bell)
Are we using food efficiently? Uses of USA corn (maize)
for every 10 ears of corn that are grown, only 2 are consumed directly by man as food. 8 are used in almost equally amounts for animal feed and for ethanol
is animal farming an efficient way of using crops?
NO 4kg - 8kg of grains in animal feed produce 1kg of meat. In Brazil, an area the size of all the agricultural land in Switzerland is used to grow soybeans to feed Swiss livestock.
3 types of biofuel
- first generation biofuels
- second generation biofuels
- third generation biofuels
first generation biofuels
primarily from food products:
- bioethanol (from starch)
- biobutanol (from starch)
- biodiesel (soya beans)
second generation biofuels
primarily from crop and forest residues and from non‐food energy crops:
-direct combustion of biomass, pyrolysis, gasification
-Cellulosic ethanol
Current technologies and costs are based on small‐scale plants only
recently commercialised.
third generation biofuels
-algae
Dedicating all U.S. corn and soybean production to biofuels would meet only
__% of gasoline demand and _% of diesel demand
12%
6%
is production of biofuels efficient?
Life cycle analysis: Farming, transport and processing all involve inputs and
environmental burdens that must be set against the energy obtained from the biofuel.
Energy yields vary. corn ethanol = 1.25
whereas sugar can biodiesel = 12-14
neither fab
EU’s aim of cutting greenhouse gas emissions by 20% by 2020 is causing a surge in palm oil demand leading to :
rainforest destruction.
- Within 15 years, 98% of the rainforests of Indonesia and Malaysia will be destroyed
- Burning forests releases large amounts of CO2
