Toxic waste routes

The project posed a series of challenges that had to be overcome in order to create a meaningful design. The data provided by the Secretariat of the Basel Convention were partial and inconsistently formatted due to lack of rigor by submitting countries.

Furthermore, the Convention's website collects an archive of all the reports submitted in the past, but the structure of the archive has changed during the years, making it difficult to easily get what we needed. The complete dataset was gathered by italian journalist Guia Baggi and later cleaned and merged with additional data (countries informations, geo coordinates, etc…) to make it accessible to work with. In the end we focused on the type and the amount of hazardous waste traded, since they were the core of the dataset as well as the most consistent data throughout the corpus.

A second issue was choosing if it was best to show only the exports, the imports or both at the same time. Even if in the overall picture representing both flows would result in doubling the data, at the country level having both informations helps to highlight behavior patterns: countries that are only exporting, countries that did not submit the annual report but show imports data based on other countries' report, etc…

Initially we also wanted to emphasize the movements of cargos between nations, in order to single out those exchanges that were taking thousands of kilometers to complete. Later on, after various attempts, the feature was dropped mainly for two reasons:

• we didn't know the actual route taken by the cargo nor the means of transportation, so the animations could have induced users to misleading assumptions;
• showing the movements on a global scale cluttered the visualization.

The last challenge was to maintain both the temporal and spatial dimensions of the phenomenon.

After a few iterations of different visual models, we went with a mixed approach: treemaps, representing the amount of waste related to each country, are arranged in space as if they were part of a Demers cartogram hence simulating as closely as possible the relative position of countries on a geographic map. This raised a new challenge: a round of user testing sessions brought up the need to bridge the gap of abstraction between the visualization and a real map. For this reason the user is introduced to the final design through a sort of tutorial where countries are first placed on a map and then “transformed” step by step in treemaps, introducing one at a time all the visual encoding variables.

The data can then be filtered by year and by category of waste.

By clicking on a single country, a more in-depth view is provided. The color of the treemap divides the imports from the exports, while the two different levels of subdivisions highlight where the waste was imported from/exported to (level 1 — solid border) and what kind of waste were moved (level 2 — dashed border).

The tool is a good first prototype for the exploration of the Basel Convention data and it let us experiment with different visual solutions, testing their effectiveness in that particular situation. We can find of course some drawbacks:

• this level of abstraction makes it difficult for the user to perceive the countries (even with the help of the tutorial);
• in order to fit all the treemaps on the screen, we had to compress all the values in a relatively small range, skewing a bit the relative dimensions of the nations. For the same reason the user has to click on each country to get that additional layer of information that would have been great to have just in one view;
• some more work has to be done to improve the performance of the tool, especially tweaking the force layout that governs the position of the treemaps.

As further steps it would be interesting to find a better way to highlight specific cargos in order to trace them better on the map, as well as adding the actual route of every waste movement with animations to have a better understanding of the phenomenon.