Thank you for taking the time to share this feedback.

I have logged this, along with other advance search feedback and issues, for the NBN Atlas development team to work on. The team have some time to work on backlog tasks, so hopefully they should have some time to look into and resolve some/all known issues with the Advance search.

Thank you again.

Kind regards,
Rhiann

[exclude] Occurrence status: "absent" 

This is implemented as a URL element:
   

fq=-occurrence_status%3A"absent"

Advanced Search does not allow this to be set either to unfiltered or to only find records where Occurrence status: "present".
The filter is shown under the category 'Selected filters' to to left of the hitlist but cannot be unchecked!

This could readily be solved by adding a section to Advanced Search. The default would not change.

Occurrence status:   

  x  Include Present         (checked by default)
  x  Include Absent          (unchecked by default)

(If both are unchecked, nothing would be found. But people would understand this.)