I was playing around with this mapping feature and made a map showing the expanding range of the spotted lanternfly since 2016, and thought others might appreciate it too.
https://bit.ly/2koSTWi
I’m a little surprised the range hasn’t expanded more in 2019 (but thankful for that I guess), but the season is not yet over.
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That’s a cool map! I wonder if it has to do with the increasing number of observers combined with the spread of those observers to new ground.
2016: 21 observers
2017: 79 observers
2018: 312 observers
2019: 419 observers
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That’s a clever application of the tool.
We are only 2/3rds of the way through 2019, so still some spreading to go…
I often wonder how much geographical variation in observation has to do with observation density vs organism density. Obviously there are more observations close to urban areas, but I don’t have the statistical chops to test total observation density to density of observations of interest.
In this case, I think the spread is real, mostly due to the connected media coverage of the new invasive species.
I agree. After I made the map I checked against the observations to the current date and saw that a good chunk of the territory “gain” in previous years also happened through the fall, so my thankfulness is probably premature.
Heres a screen shot of observations through sept 9 each year:
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Really cool! I was coincidentally giving a presentation a couple weeks ago at a BioBlitz and made a similar map, also for Spotted Lanternfly, but did it by creating annual time slices and showing the maps in succession. Worked, but I also like the color coding strategy you used.
Here’s a gif: 
Unlike many temporal patterns in iNat, this one is not a function of observer bias, it’s a real exponential expansion in an invasive species and is likely to continue to accelerate. One of the key things to watch is how the isolated outposts will expand over time. I’m thinking there is a longer-distance dispersal mechanism that is allowing new populations to colonize distant sites.
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We had harlequin ladybird arrive in NZ a few years back, and in iNat we could watch as the observations spread down the country. This map sequence shows only observations in each year, not cumulative. The spread pattern doesn’t follow the iNat use spread pattern, which is somewhat evident in the second image showing all iNat observations for NZ from 2015, where a strong participation is seen around Christchurch, Wellington and Auckland, locations that have universities and museums that have fostered the growth in iNat use early on in NZ.
I think the best inidication of the effect of iNat growth on spread patterns is to do comparable “spread patterns” for a similar native or well establshed species, which will in theory show no establishment spread so will therefore indicate only the usage growth
[edit] Have worked up a corresponding series for Adalia bipunctata:
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