Is there a significant difference in meaning between "other studies confirmed" and "other studies have confirmed" in this context?

Question

I recently corrected something for a friend. She wrote this:

An international team of scientists collected insects using the so-called “Malaise traps” in 63 protected areas in Germany. This long-term study revealed that the biomass of flying insects decreased by more than 75 percent in the time from 1989 until 2016. Other worldwide studies confirmed or even exceeded these figures.

I thought it was fine, but her teacher put a "(have)", before "confirmed" suggesting the present perfect could be used instead.

"Other worldwide studies (have) confirmed or even exceeded these figures."

I told her to ask him why since it seemed illogical to me!

"He said that she didn't give any information about the time the studies were published and it could have been the case that they were still running! I addition to that he said that it also could be a possibility that there might have been studies before 2016 that had been ignored (though correct or important) in addition to studies to after 2016."

He basically said that the sentence is unclear if I understood him correctly.

Well, I object that. First, the use of the present perfect would suggest that the studies are still running (which seems impossible since a study is by definition already finished when calling it a study (?)), and you would, therefore, have to call it an unfinished study. Second, the simple past can be accompanied by adverbs or adverbial determinations but it doesn't have to be, does it? Why should there be additional information here?

Third, the past perfect should be used in the same sentence than the simple past as far as I am concerned rather than in the next one in this case (semantically):

This long-term study revealed that the biomass of flying insects decreased by more than 75 percent in the time from 1989 until 2016. Other worldwide studies that had been conducted confirmed or even exceeded these figures but were ignored and others also confirmed or exceeded these figures."

You should probably add a "before 2016" and "after 2016" here but it seems so awkward to even write it like that?

I don´t know if he is really well educated or just picky!

Answer 1

It is conventional to speak of works (studies, poems, novels, dissertations, etc) as having present existence when we are referring to their presented content or representations, unless we are deliberately placing the works themselves in a historical context.

For example:

Early on in the science, Mendel's studies of pea plants showed ...

If a work has been superseded, or is no longer relevant to the state of the art, we would most likely speak of it using the past tense:

Those flawed studies showed that ...

as the present and present-perfect denote relevance-to-the-Present; if something can be dismissed, it is no longer relevant to our present understanding; it may be relevant to how we got to where we are today, but that is its historical relevance, not its current relevance. If you wish to speak of the study's findings as relevant to the ongoing scientific or scholarly debate, use the present perfect or present:

These studies show that ...

These studies have shown that ...

That the studies may be still running (or that the models are still being developed) may be a fact relevant to claims about what the studies show or have shown to date, but it has no bearing on whether to choose between simple past and present perfect. The choice in that case would be between present continuous, present, or present perfect, as we would not use past tense with something that has not completed:

What these studies are beginning to show ...

What these studies have begun to show ...

What these studies have shown so far ...

What these studies show so far ...