It’s been my passion – and I’m sure I’m not alone – to watch the spring progress each year, and to think about how each year compares with the ones before. This is of concern to many, many people these days as climate change strengthens its grip on our part of the world. I’ve been watching the special open water areas in the Yukon Southern Lakes that are so important to our early bird migrants, especially the Trumpeter Swans. Almost every spring since 1986 I have flown around in an airplane and taken pictures of these places on the same dates: April 24 and May 8. I talk about that photo record elsewhere on our website https://yukonbirds.ca/climate-change/. This flying costs money and I am extremely grateful to my former employer Environment Canada as well as the generosity of an American NGO called Lighthawk and local pilots David Downing and the late Gerry Whitley. I’ve also scoured through publicly available satellite images from the past 38 plus years. Satellite images are a bit problematic because regular (i.e. visible light) imagery can’t see through clouds. In addition the NASA Landsat series of satellites, which have the longest period of standard imagery, only pass over each part of the earth every 16 days. Fortunately at our high latitude the paths overlap a fair bit, so there is repeat coverage more like every 8 days. Still it’s a bit sketchy when things are changing fairly fast on the ground and many passes are obscured by clouds.
I just discovered (thank you Doug Davidge!) a series of European Space Agency satellites (Sentinel) launched in the past 7 years that offer much more frequent coverage, and have higher ground resolution than the Landsat satellites. The imagery is free to the public, and perhaps even more important, there is an extremely user-friendly web-interface that makes it easy to visualize and download samples of these images very shortly after they are acquired. Anyone can do this – you don’t need to be a techno-geek. If you can use Google Earth you should be able to handle it. You’ll find this great resource at SOAR.EARTH. (Note this link will open to images of the Swan Haven area, but you can choose to look at anywhere on earth!) WARNING: ADDICTIVE.
Here are a few of these satellite imagery gems I’ve gathered to show how spring is shaping up this year in the area of Swan Haven as compared to the previous 6 years. It’s important to note that the 2019 and 2016 images were taken much earlier in the spring than the others because there were no cloud-free images available closer to the desired date. Public satellite images are very convenient, but they can leave gaps in coverage! That’s where good old airplanes, or perhaps drones, can help. Luckily, we now have three years in a row with images on exactly the same date: