Cherry blossom blooms – and the seasons they follow – can be tracked with social media

Ever posted a picture of a tree in full bloom to social media? It could be a crucial source of data on pollination.

A team of Australian researchers has found that images of cherry blossom flowers posted to social media can accurately track the Japanese blooming season.

This makes these photos a treasure trove of information on blooming seasons, and how they’re changing with global warming.

The technique, described in Flora, could also be used to monitor other flowering plants that pollinating insects rely on.

Study co-author Associate Professor Adrian Dyer, a researcher at Monash University, says that the team first started thinking about this when the United Nations Food and Agriculture organisation published a report on pollination systems and climate change in 2011.

“The executive level summary was basically: ‘we don’t know what’s going to happen, and we need more research’,” says Dyer.

But ecologists don’t have the manpower to look at a lot of things happening in the same season.

“The logistics were: if you have a team of researchers who want to do a biology study of what’s happening in pollination, you go to one field site, and you collect data in detail,” says Dyer.

“But to understand climate change, you need to know what’s happening across an entire nation simultaneously, which is logistically impossible to do with biologists going out into the field and collecting data.”

Dedicated citizen science projects like the Wild Pollinator Count can help with some of this, but the researchers found that social media can be a rich seam of information too.

The team showed in 2017 that the distributions of two Australian insects and two flowering plants could be mapped using photos people posted to the photo sharing site Flickr.

“That told us this is a valid system: it can reliably represent a position in space of what’s occurring,” says Dyer.

They’ve now turned to Japan to see if they could map flowering plants not just in space, but in time.

“We chose Japan for this study because there’s a high density of people in a relatively small country compared to Australia. So we’re hoping we could see the actual signature of plant flower colours as they come into bloom, and how that related to the temperature of the season,” says Dyer.

The cultural importance of cherry blossoms in Japan also means that there are plenty of photos of the trees.

“The other advantage was that Japan has historic records on their flowering seasons going back for centuries,” says Dyer.

The researchers examined pictures tagged as “cherry blossoms” posted to Flickr between 2008 and 2018.

Once they’d filtered out the irrelevant pictures with AI, the researchers could use the time stamps and GPS location tags on the images to make a map of blooms across Japan.

They were able to estimate when the blooms were at their peak in different Japanese cities: peaks generally arrived earlier in the south than in the north.

The blooms happened during a 12-week period between March and May, and there was a second, smaller set of off-season blooms in November.

“We found our research results to be accurate within a few days when compared against historical flowering data published by the Japan National Tourism Organisation,” says co-author Associate Professor Alan Dorin, also at Monash.

While Japanese cherry blossoms are very popular, the researchers are confident they’ll be able to use this technique to look at other flowering seasons too.