Biodiversity on Prescott National Forest

 How many plant species are there in a geographic area?  Previously, I used iNaturalist to calculate total biodiversity for selected areas.  But this method is just a snapshot of the species currently recorded in iNaturalist.  In some areas, people may have already observed most of the biodiversity, while in other areas there may still be much more to discover.

One way to estimate the total unobserved biodiversity of a geographic area is to look at the timeline of species observations.  If more new species are being observed each year, there are likely still many more species to discover, whereas if the number of new species each year is declining, we may be able to fit a decay function that would predict the total number of species that will ever be observed.

iNaturalist offers a couple of ways to find lists of new species.  As an example, I will use the Prescott National Forest in AZ.

The first method: the API function recent_taxa.

According to this method, there have been 57* new plant species observed on the Prescott National Forest in iNat so far this year.  This is filtered for only research grade observations (quality_grade=research).  There are a lot of new observations by experts that just haven’t been confirmed by other experts. *For some reason this returns the species, genus, and family so to get 57 I subtracted repeated taxa (29) from total new taxa this year (86).

https://jumear.github.io/stirfry/iNatAPIv1_identifications_recent_taxa.html?place_id=130970&taxon_id=47126&hrank=species&order=desc&order_by=created_at&per_page=200&quality_grade=research

The URL code is pretty easy to modify for other places (PNF = 130970) and other taxa (plants = 47126).  Here is more background on API query terms: https://api.inaturalist.org/v1/docs/#!/Identifications/get_identifications_recent_taxa

The second method: download data.

 When searching observations for Prescott National Forest and filtering by plants, iNaturalist returns a page with summary statistics.   This can be downloaded and analyzed in Excel.

https://www.inaturalist.org/observations?place_id=130970&iconic_taxa=Plantae 

 After downloading the data:

1. sort the table from oldest to newest by the observation date column

2. select the whole table

3. use “remove duplicates”, and look for duplicates in only the species name column

The resulting list will show you the first observation of each species.  I then summarized the list by year and created this graph showing the year and number of new plant species recorded in iNaturalist for PNF.  

This method also sometimes returns other taxa than species, so the totals don't quite match between the website, the API, and this method.  Also, this graph is not filtered for only Research Grade observations, but it would look basically the same.  The graph appears to increase over time as more people use iNaturalist to record plant species on Prescott National Forest, up to a peak year in 2020.  Since then the number of new species seems to fall off, although it should be noted that 2021 was a drought year and 2022 isn't over yet.