IB ESS HLTopic 8 — Human PopulationsPaper 1 & 2HL only~9 min read
Environmental Migration
People have always moved for work, safety or family. Increasingly they move because the place they live has stopped being liveable — the fields have turned to dust, the sea has come over the wall, or the storm took the house. This page covers why environmental migration happens, and what it does to the people who leave, the places they leave, and the places they arrive.
📚 What you need to know
Environmental migration is the movement of people caused by environmental conditions that make living difficult or unsafe.
Sudden-onset events happen in hours or days: floods, cyclones, wildfires, earthquakes.
Slow-onset events build over years: desertification, sea-level rise, saltwater intrusion, long droughts.
Most environmental migration is internal — people move within their own country, usually to cities.
Impacts fall on three groups: the migrants, the origin area and the destination area.
There is no legal status for an environmental migrant. The 1951 Refugee Convention does not cover people fleeing environmental change.
Environmental causes almost always mix with economic and political ones, so the label is rarely clean.
Two speeds of disaster
The single most useful split in this topic is how fast the trigger arrives, because it changes everything about how people move and whether they return.
Sudden events often produce temporary displacement close to home. Slow-onset change produces permanent moves, usually towards cities.
Sudden-onset causes
Flooding. Heavy rainfall or rising rivers force people out of their homes, sometimes for a season, sometimes for good. Bangladesh sits on a huge delta and experiences displacement from flooding almost every year.
Cyclones and storms. Wind and storm surge destroy housing and infrastructure. Mozambique was hit by Cyclone Idai and Cyclone Kenneth in 2019, and hundreds of thousands of people were displaced within the country and across borders after homes and farmland were destroyed.
Wildfires. Fires destroy homes, farmland and infrastructure and force rapid evacuation. The Australian bushfires of 2019 to 2020 forced thousands to leave affected regions.
Slow-onset causes
Desertification. Arid conditions spread, soil fertility falls, and farming stops paying. In the Sahel, families move to urban centres or across borders when the land can no longer feed them.
Sea-level rise. Higher seas mean bigger storm surges and, eventually, land that is permanently under water. Low-lying Pacific nations such as Tuvalu face this directly, and migration to countries such as New Zealand is already happening.
Saltwater intrusion. Salt water pushes into groundwater and farmland near the coast, cutting crop yields. In coastal Bangladesh this drives rural families towards cities, and a great many end up in Dhaka, adding pressure to housing and services that were already stretched.
Notice that all three slow-onset causes end the same way: farming stops working, so people move to a city. That is why this topic leads straight into urban systems. Rural environmental stress is one of the main engines of urban growth.
Who is affected, and how
Cover all three columns in a long answer. Most candidates write about the migrants and stop, which caps the mark.
The legal gap
This is the point that lifts an answer. Someone fleeing persecution can claim refugee status under the 1951 Refugee Convention. Someone whose island is disappearing cannot, because environmental change is not a listed ground. The phrase “climate refugee” is common in the media but has no legal meaning, so environmental migrants often have no right to protection, to work, or to stay.
Environmental causes are rarely alone. Drought reduces harvests, which reduces income, which raises food prices, which can trigger conflict. By the time someone leaves, it is almost impossible to say the cause was purely environmental. Saying this shows the examiner you understand the limits of the category.
WORKED EXAMPLE
Classify each of the following as sudden-onset or slow-onset, and state the likely pattern of movement: (a) a cyclone destroys coastal villages; (b) groundwater in a farming district becomes too salty to irrigate with.
(a) CycloneSudden-onset. Movement is forced and immediate, usually short distance and internal, and some people return once housing is rebuilt.
(b) Saltwater intrusionSlow-onset. Farming income falls year by year until families give up, so movement is gradual, usually permanent, and directed towards cities.
Sudden causes displacement; slow causes relocationAdding whether people are likely to return is what turns a classification into an explanation.
WORKED EXAMPLE
Rural families in a low-lying coastal region are moving to the capital city in large numbers because of saltwater intrusion. Outline the impacts on the origin area and the destination area.
Step 1: origin area
Farmland is abandoned and villages shrink. Young adults leave first, so those who stay are older and the workforce collapses.
Some money is sent back, which supports those who remain.Step 2: destination area
Rapid arrivals put pressure on housing, water supply, sanitation and schools, so informal settlements expand on the city edge.
The city also gains a large supply of labour.Step 3: the link
Rural environmental stress becomes an urban planning problem.
One environmental change, two very different sets of consequencesGiving one positive alongside the negatives shows balance, which “outline the impacts” is quietly asking for.
💡 Exam tip
Learn one named example for each cause. A country and a rough date is enough.
Always classify the event as sudden or slow-onset first. It structures everything you write afterwards.
Cover all three impact groups: migrants, origin, destination.
Include at least one positive impact, such as money sent home or extra labour, so your answer is balanced.
Mention that most environmental migration is internal. Many candidates assume it is all international.
Bring in the legal gap. It is precise, memorable, and very few students use it.
⚠ Common mix-ups
Calling environmental migrants refugees. Refugee is a legal category that does not currently cover them.
Assuming everyone crosses a border. Most moves are within the same country, usually rural to urban.
Treating slow-onset events as less serious. They displace far more people than sudden disasters do.
Blaming migration on one cause. Environmental, economic and political pressures almost always combine.
Writing only about the migrants. Origin and destination areas carry half the marks.
Naming no examples. “A country hit by flooding” is worth far less than “Bangladesh”.
Up next: What Makes an Area Urban — the first page of 8.2, on where all these rural migrants end up and how a city works as a system.
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