Syllabus Edition
First teaching 2024
First exams 2026
Climate Change & Ocean Acidification (DP IB Environmental Systems & Societies (ESS))
Revision Note
Written by: Alistair Marjot
Reviewed by: Bridgette Barrett
Climate Change & Ocean Acidification
What is climate change?
Climate change refers to significant changes in global temperatures and weather patterns over time
Mostly driven by human activities such as burning fossil fuels, deforestation and industrial processes
Leads to global warming, which is an increase in Earth's average surface temperature
What is ocean acidification?
Ocean acidification is the ongoing decrease in the pH of Earth's oceans
Caused by absorption of excess carbon dioxide (CO2) from the atmosphere
When CO2 dissolves in seawater, it forms carbonic acid, which lowers the pH
Impacts on ecosystems
Climate change effects
Temperature rise:
Warmer waters can alter habitat ranges for marine species
For example, many fish populations are migrating to cooler waters, impacting local fishing industries
Melting ice caps:
Polar ice is important for the survival of many species
For example, the loss of important ice habitats will affect polar bears and seals that need them for hunting, avoiding predators and raising offspring
Walruses are increasingly forced to rest on land, leading to overcrowding and increased mortality
Leads to sea level rise, threatening coastal ecosystems
For example, rising sea levels are threatening the coastal mangrove forests in Bangladesh, which serve as crucial habitats for many species and protect the coastline from erosion
Hurricane damage:
Increased intensity and frequency of hurricanes is damaging coral reefs (e.g. in the Caribbean)
For example, hurricane Irma in 2017 caused widespread coral destruction, particularly affecting the coral reefs around the Florida Keys and the Virgin Islands
Ocean acidification effects
Coral bleaching:
Warmer temperatures and acidification cause coral to expel the algae that live in their tissues
This causes the coral to turn white (known as bleaching)
This often leads to coral death if the stressful conditions persist
For example, the Great Barrier Reef is currently experiencing massive coral bleaching events
Shellfish vulnerability:
Acidic waters weaken calcium carbonate shells of marine organisms like oysters, clams, and sea urchins
This makes them more vulnerable to predation, disease and environmental stress,
This can lead to population declines and disruption of marine food webs
For example, oyster populations in the Pacific Northwest (USA) are in decline partly due to ocean acidification
Oyster farms here are struggling with reduced harvests due to shell degradation
Case Study
The Great Barrier Reef
Location and importance
Located off the coast of Queensland, Australia
World's largest coral reef system is home to diverse marine life
Supports tourism and fishing industries, crucial to the local economy
Stress factors
Coral bleaching events:
Repeated bleaching events have caused significant damage
In 2016 and 2017, back-to-back bleaching events affected two-thirds of the reef
Rising sea temperatures:
Even very small increases in temperature can trigger bleaching events
Ocean acidification:
This is weakening coral structures, making them more susceptible to erosion and breakage
Wider impacts on the ecosystem
Biodiversity loss:
Coral reefs support many marine species
Coral bleaching leads to the loss of habitat and food sources for these organisms, resulting in decreased biodiversity
Fishing industry:
The Great Barrier Reef supports commercial and recreational fishing industries
Coral bleaching reduces fish populations, affecting the livelihoods of local fishermen and the economy
Tourism:
The reef is a major tourist attraction, bringing in millions of visitors annually
Bleached and dying corals reduce the aesthetic and ecological value of the reef
This leads to a drop in tourism revenue
For example, snorkelling and diving tours experience decreased interest as the vibrant coral ecosystems become bleached and lifeless
Coastal protection:
Coral reefs act as natural barriers, protecting coastlines from storm surges and erosion
Damaged and weakened reefs are less effective at buffering waves, leading to increased vulnerability of coastal populations
For example, communities along the Queensland coast are facing higher risks of flooding and property damage due to weakened reef structures
Marine food web disruption:
Coral reefs are integral to marine food webs
Bleaching disrupts these webs by removing key species and altering predator-prey relationships
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