IB ESS SLTopic 4 — Aquatic Food Production SystemsPaper 1 & 2Core idea~9 min read
Rising Demand for Seafood
Humans have always eaten what they could pull out of the water. What has changed in the last sixty years is the scale: global consumption of aquatic food has more than quintupled. Understanding why is the setup for everything that follows about overfishing and fish farming.
📚 What you need to know
Humans consume aquatic flora and fauna from both freshwater and marine environments.
These provide essential nutrients and are a significant part of many cultures’ diets.
Consumption patterns vary locally and globally, reflecting availability, tradition and sustainability concerns.
Demand has increased sharply over the last 50 to 100 years.
The main drivers are population growth, changing diets, the nutritional value of seafood, urbanisation and a growing middle class, global trade, and the expansion of aquaculture.
Since roughly 2010, aquaculture rather than wild capture has supplied most of the growth.
What people actually eat
Exam questions on this often ask for local and global examples, and for both flora and fauna. It is worth having a few of each ready.
Organism
Flora or fauna
Environment
Reach
Notes
Watercress
Flora
Freshwater
Local
Leafy green grown in shallow flowing beds fed by springs; popular in the UK in salads and soups
Spirulina
Flora
Freshwater
Global
A cyanobacterium grown in ponds and lakes, filtered out and dried, sold worldwide as a supplement
Dulse
Flora
Marine
Local
Red seaweed hand-picked from rocks at low tide, dried, and traditionally eaten in Ireland
Nori
Flora
Marine
Global
Red seaweed farmed on nets in coastal water, dried and pressed into sheets; central to Japanese cooking
Trout
Fauna
Freshwater
Local
Raised in ponds or tanks with controlled water quality and netted at market size
Tilapia
Fauna
Freshwater
Global
Farmed in ponds or recirculating systems worldwide; cheap, fast-growing protein
Scallops
Fauna
Marine
Local
Hand-collected by divers from the seabed, for example around Orkney, which limits seabed damage
Shrimp
Fauna
Marine
Global
Raised in coastal ponds or tanks and harvested by draining or netting; traded worldwide
Notice the pattern. The “local” examples are gathered or grown at small scale; the “global” ones are farmed and traded. That single observation answers a lot of questions about why demand has grown the way it has.
How much demand has grown
Describing this in an exam: consumption rose steadily from about 30 million tonnes in 1960 to roughly 160 million tonnes by 2020, with the rate of increase accelerating from around 1990 onwards.
Why demand rose
Growing human population. More people means a larger consumer base for the same finite resource.
Changing dietary patterns. As economies grow, diets tend to shift towards protein-rich foods, including seafood.
Nutritional value. Seafood is recognised as a good source of omega-3 fatty acids, vitamins and minerals, all linked to health and wellbeing.
Urbanisation and a rising middle class. More people with more disposable income want more varied, higher-value foods.
Global trade and supply chains. Better transport and refrigeration mean seafood can be imported and exported far from where it was caught.
Aquaculture. Farming has grown enormously, and by supplying more it has also made seafood cheaper and more available, which raises demand further.
Where the extra fish comes from
This is the graph that matters most. Wild capture for food has been roughly flat since the 1990s — the ocean simply cannot give more. Every additional tonne now comes from farming.
The green bars flattening out is the story of the next page: wild stocks have hit their ceiling. The red bars overtaking them is the story of the page after that.
If a question gives you this kind of chart, describe both series separately before comparing them. “Capture rises then plateaus after 1990, while aquaculture rises continuously and overtakes it by 2020” is a complete answer in one sentence.
Worked examples
EXAM Q1
Outline three reasons for the increase in global demand for seafood. [3]
Reason 1: population
A rapidly growing global population means more consumers for the same resource.
Reason 2: wealth and diet
Economic growth and a rising middle class shift diets towards protein-rich, higher-value foods.
Reason 3: availability
Better transport and global trade put seafood on sale far from where it was caught.
More people, richer diets, wider availabilityhealth benefits and aquaculture growth are equally valid third points
EXAM Q2
Using the bar chart above, describe how the sources of aquatic food changed between 1970 and 2020. [3]
Step 1: capture fisheries
Rose from about 39 to 70 million tonnes, but growth slowed sharply and levelled off after 1990.
Step 2: aquaculture
Rose continuously from under 5 to about 88 million tonnes.
Step 3: compare
Aquaculture overtook capture fisheries by 2020 and now supplies most of the growth.
Wild capture plateaued; farming took overquote figures for both series — “describe” questions are marked on data use
💡 Exam tip
Have one local and one global example of both flora and fauna ready. Nori and tilapia are global; dulse and watercress are local.
When describing a graph, always quote figures and name the year the trend changes.
Say aquatic food rather than just “fish” — seaweed and shellfish count too.
Link demand to population plus income. Neither alone explains the curve.
Note that seafood demand is a consumption issue as well as a production one; diets can change.
Use the plateau in wild capture as evidence when arguing that fisheries are at their limit.
⚠ Common mix-up
Assuming all seafood is wild-caught. Most of the growth since 2000 has been farmed.
Treating seaweed as a curiosity. Nori and spirulina are major global foods.
Explaining the rise by population alone. Consumption per person rose too.
Confusing “demand” with “supply”. Demand kept rising after wild supply stopped.
Ignoring culture. What people eat is shaped by tradition, not only by income.
Describing a graph without data. “It went up” earns nothing.
Up next: Overfishing and Damaging Harvest Methods — what happens when demand keeps rising after the wild supply has stopped.
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