CLD9017 Ecology: The Science of Environmental Issues
Climate Change
Hui Tin Yan
Science Unit
tinyanhui@ln.edu.hk
LCH112
L13: Climate change
• Identify, describe, and apply knowledge about ecological
concepts that underlie environmental issues affecting human
societies.
o Understand and describe some key contributors to climate change
o Understand and describe the consequences of climate change
• Critically evaluate of news and/or media pieces pertaining to
ecological and/or environmental issues. This includes the
ability and confidence to produce well-reasoned opinions
about the issue, both orally, as well as in writing.
o Identify “climate denialism” and the arguments that underly the
movement
Climate change
• Anthropogenic climate change is caused by increasing
greenhouse gas concentrations in the atmosphere.
Bailey et al (2015)
What is greenhouse effect?
• Water and greenhouse gasses in the atmosphere absorbs
and retains heat from the sun.
Recall the role of CO2 in primary production
• Carried out by autotrophic organisms
• Most common form of primary production is
photosynthesis:
o Chemical reaction involving chlorophyll within the chloroplasts of
plant cells
CO2 + H2O + sunlight → glucose + oxygen
© Brittany
© JamesGunther
St. John
Sources of greenhouse gas
• Since the industrial revolution, humans increasingly power
the world with fossil fuel.
• Most greenhouse
gasses are from
energy use followed
by agriculture.
Sources of greenhouse gas
• The U.S.A. and China biggest sources of CO2 emissions.
Fossil fuels
• Coal is the major contributor of CO2. What is coal?
• Fossil fuels are not a renewable resource. Why?
Effects of climate change
• Major effects of climate change on the abiotic environment:
o
o
o
o
o
Increased temperature
Receding glaciers
Higher frequency of extreme climate events (e.g., droughts)
Rising sea levels
Ocean acidification
© Montree Hanlue
Temperature as a fundamental driver for biology
9
8
6
David Poon
Heart rate (Hz)
7
5
4
Parasesarma continentale
3
2
1
0
20
30
40
Body temperature (°C)
Temperature as a fundamental driver for biology
Thermal performance curve
- Metabolism
- Growth
- Survival etc
Wagner et al. 2023 PNAS
Temperature as a fundamental driver for biology
Body temperature
Upper limit
Individual can
“fight” or “flight”
Lower limit
Environmental temperature
Ng et al. 2017 JEMBE
Higher temperature shrink species range
• Hotter temperatures change habitat range:
o Latitudinal shifts (move away from the equator)
o Altitudinal shifts (move to higher ground)
• This is more impactful for some species than others. Why?
Urban (2018)
It matters!
Climate niche of
coffee species
Coffea stenophylla
Davis et al. 2021 Nature Plants
It matters!
C. stenophylla
produces good
flavour as arabica,
but can be planted
in warm climate as
in robusta
Davis et al. 2021 Nature Plants
Rising temperature in the ocean
• Coral bleaching if species are associated with heat-sensitive
zooxanthellae.
• Climate change may increase frequency of extreme heat-waves
• Nowhere to escape! (compared to terrestrial env. with shades,
different altitudes etc)
•
Long, cross-latitudinal shifts
Impacts of temperature on reproduction
• Sex-ratio skewed for species with temperature-dependent
sex determination (recall previous lectures on sex ratio).
• Temperature change disrupts breeding seasonality. How
does this impact species survival?
Biogeographical shifts in community
• Effects on ecosystem services, fisheries, other food security,
cultural values etc
Pecl et al. 2017 Science
Biogeographical shifts in community
Examples of climate-driven changes in the distribution of species
throughout marine, terrestrial, and freshwater systems of the globe
in tropical, temperate, and polar regions
Pecl et al. 2017 Science
Biogeographical shifts in community
• Mean Temperature of the Catch (MTC)
• Average thermal preference of caught individuals (recall that there
will be different species within a community)
Extreme events
• Climate change increases frequency of extreme events
(e.g., droughts, floods).
• This can be caused by disruptions to ocean circulations
(e.g., El Niño Southern Oscillation).
• Droughts increase
frequency of forest
fires.
Extreme events
• Extreme storm surges threatening coastal zones
• Typhoon Mangkhut in 2018
• Severe disturbance events => impacts on the ecology?
Extreme events & mortalities
• Biodiversity can be threatened directly and indirectly.
• E.g., Australian forest fires killed plants and animals directly
• E.g., Indonesian forest fires caused haze which killed insect
pollinators.
Extreme events & mortalities
• Biodiversity can be threatened directly and indirectly.
• E.g., “slow cook” of bivalves and snails in the intertidal zone
Extreme habitat temperature
Mussel mortality in South Lantau
Rock temperature (°C)
70
65
60
55
50
45
40
35
30
25
20
22/8/2021 0:00
23/8/2021 0:00
24/8/2021 0:00
25/8/2021 0:00
Date & time
26/8/2021 0:00
27/8/2021 0:00
Rising sea level impact key ecosystems
Rising sea level impact key ecosystems
Melting of ice + thermal expansion
Rising sea level impact key ecosystems
• Mangrove forests are
most at risk.
• Feedback effect because
mangroves are carbon
stores.
Gilman et al (2007)
Rising sea level impact key ecosystems
Future coastal zone
scenarios for Mai Po
Nature Reserve
Wikramanayake et al. 2020 PLoS ONE
Climate change and melting ice
• We can’t change the melting point of ice.
• Ice is melting on land and ocean. Melting of land ice leads to rising sea
levels
• Melting ice also contributes to feedback mechanisms:
o Retreating glaciers allow the breakdown of frozen organic matter
o Less ice means less heat from the sun is reflected into space (albedo
effect)
Climate change causes ocean acidification
• Higher concentrations of atmospheric CO2 decreases the
pH of seawater.
Climate change causes less O2 in the ocean
• Reduced solubility of O2 in water under higher
temperatures
• When combined with the effects of temperature in
metabolism …?
Drop in the
metabolic index
(ratio between
supply and
demand of O2)
Deutsch et al. 2015 Science
What are we doing about it?
• Climate change is a global issue, requiring international collaborations
• IPCC (Intergovernmental Panel on Climate Change) assesses the
science of climate change to recommend policies.
• The United Nations
Framework Convention on
Climate Change
(UNFCCC) holds yearly
conferences (e.g., COP26)
to negotiate international
treaties for reducing
greenhouse gas
emissions.
o E.g., Kyoto Protocol,
Paris Agreement
o Current target is to limit
temperature increase to
below 2°C
Sustainable Development Goals
• Goal 13 Climate action
• Key targets:
• Strengthen resilience to climate-related hazards by integrating
climate change measures in policies and improving education on
climate change
• Supporting developing countries by joint commitment from
developed countries - $100 billion USD annually (inequality
issues)
Global inequality
• Not all countries can afford to contribute equally (e.g.,
developed vs developing countries)
Towards equality
• Kyoto Protocol formalises quotas on greenhouse gas
emissions.
• Countries that exceed their quotas can purchase unused
quotas from other countries.
• Developing countries with large forests but relatively low
emissions can sell carbon credits to other countries.
• Issues with “climate change refugee” – in low-lying coastal
zones or islands threatened by sea level rise
Climate denialism
• Term to describe movement dismissing scientific evidence
that climate change is caused by humans.
• Common arguments:
o CO2 is not increasing
o CO2 increase has no
impact on climate
o Climate warming is due to
natural causes
o Human impact too small to
cause climate change
Lee et al (2015)
Climate denialism
Ignorance on sea level rise
The planet can survive climate change, but
we will not (COP26)
Can we fix climate change?
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