Method and limits

What the lines and scores mean, where the material comes from, and what it cannot tell you.

Tie strength

Every link between two states carries three expert-judgement scores from 1 to 10:

Tie strength is 0.45 × intensity + 0.25 × duration + 0.30 × legacy. On the map it sets line thickness, and the scale is non-linear so that the strongest ties stand out. The weights are a design choice, not a finding. The detail panel shows all three components, so you can disagree with them.

Link types

Colonial and imperial legacy (solid line); intervention and military power (dashed); economic dependency and trade (dotted); ideological and revolutionary ties (dash and dot); borders and migration (short dashes); and alliance and integration (long and short dashes). Two states can share several links of different types, and the globe bends each one separately so that none hides another.

Arrows and direction

An arrowhead shows who acts on whom: a metropole on its colony, an intervening power on its target, an investor or patron on a dependent economy, or the main flow of migrants. A tie with arrowheads at both ends is mutual (an alliance, a border dispute, a war between peers) or could reasonably be read either way. Each direction was assigned by reading the tie's description, so it is a judgement, like the strength scores.

History-to-climate pathways

For each state the atlas records a few causal chains from a political or historical driver (a state oil monopoly, a military road-building programme, a debt crisis) to a climate-relevant outcome (emissions, land use, vulnerability or policy). Each pathway has a direction, a strength score and a confidence rating. Indicators appear only where the order of magnitude is well established, and they are approximate.

The four modules

The atlas follows four Institute of the Americas modules, read from their UCL Moodle pages for 2026/27:

• AMER0074/AMER0078 History and Politics of Latin America c.1930 to the Present
• AMER0038 Encountering the Americas: Key Themes and Concepts
• AMER0039 Introduction to Politics
• AMER0050/AMER0051 The Making of Modern America: The United States since 1920

Each unit has an era and a set of countries. Choosing a module under "Module lens" on the Atlas page shows every tie that touches the countries its units name, in those units' eras. Choosing a unit narrows the map to that unit's era and states. The search box filters ties by country, event or theme. Units that cover the whole hemisphere show every tie from their period. Study-skills sessions are listed on the Modules page but have no map lens.

Sources and process

• Course structure: unit titles, lecturers, eras and seminar questions as listed on Moodle. Each module links back to its Moodle course page.
• Web sources: the pages that were opened to check each dossier, tie and climate profile are listed, with links, on the Sources page, together with the scholarly references named in the data.
• Country, link and climate data: written from the historical and environmental-history literature, then checked claim by claim by a second pass that corrected or removed anything it could not support, and edited for grammar, spelling and diacritics. References are listed per link and per pathway where available.
• Map: Natural Earth boundaries from the world-atlas package, drawn as a rotating globe with D3. The interface is black and white. On the globe, each country has its own outline colour, and ties are drawn as gradients between the two countries' colours.

Known gaps

• Coverage is the independent states of the Americas plus Puerto Rico, from the United States and Canada to Uruguay and the eastern Caribbean. Other dependent territories and some small states are not yet included.
• Boundaries are drawn at their modern positions, even for periods when they were different.
• The scores reflect one reading of the literature. Historians would reasonably score some links differently.
• This site supports study. It is not a substitute for the reading lists, and it should not be cited in assessed work. Verify claims in the original sources.

Open source

The Americas Atlas was made by Lazaros Tsela and is open source. Anyone may use, study, copy and adapt it, and corrections or additions are welcome.

• Code (the HTML, CSS and JavaScript): MIT licence. See the LICENSE file.
• Written content (country dossiers, ties, scores and climate pathways): Creative Commons Attribution 4.0 (CC BY 4.0). Credit "Lazaros Tsela, Americas Atlas".
• Course material: unit titles, seminar questions and reading lists are quoted from UCL Institute of the Americas module pages for study and reference. They remain the work of UCL and the module teams and are not covered by the licences above.
• Map data and libraries: Natural Earth (public domain), D3, topojson and flag images from flagcdn.com, under their own licences. See the Sources page.

The atlas is an independent student project. It is not affiliated with or endorsed by UCL. Tie strengths are expert judgements, not measurements, so check the sources before citing anything.

Contributing. The data lives in plain JavaScript files in the data/ folder, one file per region or topic. Each record names its sources. To fix an error or add a tie, edit the relevant file and include a source for the change.