I think he collects data and studies samples and he's using it to do crazy biochemical engineering stuff the way Maru is doing crazy Robotics stuff. He says a "scientist" because it's simpler than "research environmental engineer" or whatever his full title is.
He THINKS he's basically an ecologist. He just LIKES ecology. He's one of those guys who assumes that because he's an expert in maths and physics, that makes him an expert in everything else. This is also evidence that he is an engineer.
MY EVIDENCE:
- 🍅 THE TOMATO FRUIT DEBATE: DUDE, IF YOU WERE ANY KIND OF EXPERT IN PLANTS YOU'D KNOW FULL WELL BY NOW THAT "VEGETABLE" IS AN ARBITRARY CULINARY TERM AND MANY "FRUITS" ARE NOT ACTUALLY PLANT FRUITS.
-Demetrius, why are you doing this to your wife, you're an adult man, you should KNOW about peppers. And eggplants. And pumpkins. And cucumbers. And like, a bunch of nuts. If you'd studied this at college then you would have come to terms with it a long time ago.
- Stuff we see him doing: Putting bats/mushroom boxes in your farm cave, muttering to himself about nitrate levels and adjusting graphs, taking samples of soil and plant matter. Never says anything about his theories or his area of experience. Behaviour of an environmental engineer (or a lab tech) as well as an ecologist.
- "Why do humans enjoy spicy food? It's counter-intuitive from a biological perspective. Unless there's something I'm missing..." Dude if you'd really studied zoology you'd know animals are up to this kind of thing with weird chemicals all the time, humans sensation seeking with capsaicin is pretty intuitive.
- I can't find the quote but I'm PRETTY sure he says something like "How do plants know it's the correct time of year to flower?" when he should know it's daylight hours based on the length of the night.
- Muses about better dealing with his wife's mood pattern using a graph. Does not seem like someone who's dealt with something as sticky as wild animal behaviourism would say, but very engineer brained.
- Most of the time he says something scientific it's mathematical and/or related to soil analysis (nitrates, nematodes, seasonal pH).
- Did he invent the mushroom and bat boxes he installs in your caves? Like invented them like engineered them?
Disclaimer: I have reasonably warm feelings towards Demetrius and I'm aware that the reason he's like this is because ConcernedApe didn't know any of this stuff. I actually do genuinely think about this to enjoy the character more.
TL;DR: Demetrius is an environmental engineer who works closely with ecologists and he emails those guys his theories about melons and they're like, "That's not how it works. But whatever, man, you invented the Mushroom Box that generates Forever Mushrooms."