Below the small village of Zagradec near Grosuplje, Slovenia, lies a typical karst field called Radensko polje, with meandering streams dissapearing into sinkholes and caves. The streams are prone to overflow, so much of the area is swampy and thus an important habitat for rare and endagered flora and fauna.

(Part of Radensko polje in 2006. Photo courtesy of Wikipedia user Tcie.)

But this fragile ecosystem is under attack! There is a foreign invasion going on, literally suffocating the indigenous plants, driving out the animals and critically reducing the biodiversity of the area.

(Invaders on Radensko polje today.)

(Northern part of Radensko polje with Podlomscica stream as seen from a kite.)

(Radensko polje from a kite – do you see the dark lines? It’s THEM!)

Assesing the environmental impact of invasive plants begins with a simple process: count the bastards!

Since we don’t have the patience to waddle through the marsh and count every invasive plant, but we do have a kite or two, we devised an experiment – after we’ve seen something interesting in the kite aerial photos of Radensko polje.

See the dark lines crossing the field in the photo above? As the sun was low on the horizon (the light coming from the left of the photo), those lines had to be shadows – shadows of something rather tall. It is the invasive Canadian goldenrod, Solidago canadiensis, creeping upon the fragile marshy habitat, creating vast, dense stands where only other goldenrods can thrive.

Canadian goldenrod is a tall plant, up to 2 meters high. It is one of the most devastating invasive weeds in Europe, China and Japan, destroying habitats, fields and orchards, driving other species to (local) extinction.

So we asked ourselves – is it possible to take an aerial photo at the right time (late afternoon, when the shadows are tall), select an area, and determine the number of invasive goldenrods simply by counting the shadows?

Well, yes … 🙂

(Part of the previous photo enlarged. The artificial colour makes the shadows stand out – with a truly ‘scientific’ effect.)

We took that photo, fiddled with it a little, and uploaded it in the first online object-counting app we found (aptly named

The results:

There are so many invasive Canadian goldenrods here!

Of course, this is not a definitive result – more a proof-of-concept. We wanted to show that the kites can be used for ecosystem monitoring, being a cheaper, eco-friendly alternative to planes, helicopters and drones. When you study a fragile ecosystem, you joust don’t go buzzing above it, scaring all the endangered animals out …

If anyone is interested, we and our kites will be glad to participate in something like this! 🙂

Kite aerial photos made with Canon A810 on a Rokkaku kite.

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