Each year around mid-summer, somewhere between December and mid-January, the skies of South Africa’s Gauteng province, including the city of Johannesburg, fill with small white butterflies. Some land in people’s gardens, allowing a closer look at the thin brown markings on their wings. Those markings give the butterflies their name: the brown-veined white butterfly .
Climate change is intangible to many people. We know it is happening, but our larger surroundings look the same – for now. It’s difficult to feel the 1.1°C post-industrial global temperature increase. But we do notice when the jacarandas flower earlier or butterflies arrive in our gardens earlier. This is important in raising public awareness regarding climate change.
These print and social media records are a gold mine for phenologists. For our research we recorded the date of newspaper articles and social media posts relating to sightings of these butterflies in Johannesburg and used this to quantify changes in the timing. The reason for the advance in timing relates to complex relationships with climate. The strongest statistical relationship that we found in this study was between the arrival dates and the combination of minimum temperature and precipitation during December, which for the majority of the dataset was the month either before or during the migration.