I am guessing by the way it has been used in these example sentences that it can mean both a field of study and an academic paper? Is that correct? eg "The study of ruminant ecology" vs "This study shows that methane from bovine eructation is a significant contributor to climate change."
Almost. It's actually two words, only they're very similar.
en studie for a scientific paper or a specific investigation
Denna studie visar … 'This study shows …'
ett studium for 'the act of studying something'
Stor vikt läggs vid studiet av sambandet mellan … 'Great emphasis is placed on the study of the connection between …'
So it's Studiet av idisslares ekologi with a t.
en studie, studien