2

I am trying to work out how many species are within certain boundaries (ie. states) as well as find the average of the environmental factors (like rainfall). I am using:

  1. A map of Australia broken down into boundaries (polygon)
  2. 2x layers full of species data including lat long and various environmental data. (points. Every point is a single encounter record of a species including their corresponding data. There is hundreds of thousands of points so cannot use Excel).

There are 310 species, and I need to work out how many are in each state, not how many records. I have tried summarising the table but it counts the individual encounter records as opposed to an individual species. I have tried aggregating the points into a polygon (I have done it with similar datasets that were both polygons) but lose all the corresponding data in the process and it was very time consuming for 310 species.

I have tinkered around but haven't hit the winning spatial join combination yet. I have managed this in the past, with this exact data set but I had to alter it and therefore repeat it but silly me didn't write down how I did it. I know it is possible.

Visual example in textform (each letter equals a dot point)

State 1: aaabbc = 3 species (including the average rainfall etc for each individual species)
State 2: abcccd = 4 species 
State 3: abccde = 5 species

With a final table looking something like

State 1 - How many species - Avg rainfall, Avg altitude, etc
State 2 - How many species - Avg rainfall, Avg altitude, etc
State 3 - How many species - Avg rainfall, Avg altitude, etc
3
  • Some questions: What software are you using? Do each of the points in the data have the environmental data you want to keep? In the final table, are you wanting all the environmental data - so if there are 100 species, you want 100+ environmental data as well? Mar 21, 2022 at 3:29
  • Dissolve or summarize by state, specie to multipart. Do frequency on state, answe is no of species per state.
    – FelixIP
    Mar 21, 2022 at 3:33
  • ArcMap 10.6.1. All points include the environmental data for when the occurrence was recorded. Yes, the average of the species for that state.
    – Kathleen
    Mar 21, 2022 at 3:54

1 Answer 1

2

You can use a spatial join or an intersection to extract the state name for each encounter. Then using summary statistics with "state" and "species" as case fields, you can get your average environmental condition per species per state. Then you can count the entries per state, which will give you the number of species per state.

So you end up with two tables:

State_name Species Average_precipitation
State 1 Species 1 Avg rainfall spc 1
State 1 Species 2 Avg rainfall spc 2
State 2 Species 1 Avg rainfall spc 1

and

State_name Number_of_species
State 1 nb species in state 1
State 2 nb species in state 2

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.