Bdtyk

Why is "Nature" usually spelt with an initial capital letter in scientific journals? I am mainly referring to life science here, in case this matters.

I am not talking about the obvious cases, like capitalisation in titles, at the beginning of a sentence, etc., but when it appears mid-sentence, where one would normally expect it to be lowercase.

I've heard some explanation that it gives the impression of Nature as a goddess (see comments on this post here) - but this is probably the last thing I would have expected in a scientific article...

There is no hard-and-fast rule on capitalizing the word "nature" as it is not classified as a proper noun. The reason we capitalize the proper noun is to differentiate it from other common (non-proper) nouns as it is

a noun that in its primary application refers to a unique entity, such
as London, Jupiter, Sarah, or Microsoft, as distinguished from a
common noun, which usually refers to a class of entities (city,
planet, person, corporation), or non-unique instances of a specific
class (a city, another planet, these persons, our corporation).

When you capitalize such words as "god" and "lord", you no longer think about their common attributes or characteristics, but you conjure up only one entity in your mind called God and Lord.

According to the linked Wikipedia article about capitalization:

Many European languages traditionally capitalize nouns and pronouns
used to refer to God, including references to Jesus Christ
(reverential capitals): hallowed be Thy name, look what He has done.
Some English authors capitalize any word referring to God: the Lamb,
the Almighty; some capitalize "Thy Name". These practices have become
much less common in English in the 20th and 21st centuries.

If you think Nature is as unique as other proper nouns and it was created by God, there is no reason that you can't capitalize the word nature. However, when you are referring to *the basic or inherent features, character, or qualities of something", you should not capitalize it. You could only capitalize it when it means

The phenomena of the physical world collectively, including plants,
animals, the landscape, and other features and products of the earth,
as opposed to humans or human creations

It will largely depend on your personal style and preference whether to capitalize "nature" or not. You capitalize it only to emphasize its uniqueness.

[Wikipedia, Oxford Online Dictionary]

The Nature with capital "N" is a divine or ultimate force that controls the universe. Otherwise, nature with small "n" is for common use like "This is a part of his nature" or "It is quite natural to be feel angry at times".