Discussing climate change is a repetitive matterredundant.

It has been known for a while that this is rather thannot just weather change, it's something long-term and progressive and. It leads to flood, drought and sea levels rising in some regions.

However, alongsidwhile the glaciers are melting, more land and new nautical routes will be discovered, which will bring a potential huge fortune in these new areas.

It's probably one of the key reasons that American President Trump is seelooking the realm ofo annex Canada and Greenland.

Discussing climate change is a repetitive/boring matter.

It has been known that this is, rather than simple weather change, it's something long-term and progressive andwhich is leadsing to flood, drought and sea level rising in some regions.

DThe discussingon of climate change is a repetitive matter.

Generally a « matter » is about an object which can easily be fixed by basically talking about the action of discussion as an object but when saying « discussing » you are talking about an action which will sound slightly wrong it would be better to say « Discussing climate change feels so repetitive »

This is actually very difficult to explain because the second line sounds significantly less formal and a formal version would be « Climate change is a very repetitive topic to discuss »

But the basic tip if you want to call something a « matter » it’s better to objectify it a general tip to do that is to find an alternative to the continuous « -ing » tense however this is not a grave offense

It has been known that this topic is rather thanslow/ is ,unlike weather change, it's something long-term and progressive and leads to flood, drought and sea level rising in some regions.

For this section it’s about your intent do you want to compare it to weather change then you should place a comma « , » between as it’s effectively not necessary for the sentence. So it’d be « climate change, unlike weather change, happens slowly » the sentence can work without the the line comparing it to weather change so it’s placed in between commas. If you want to use rather as a pre-adjective then it needs to be placed there. Rather can only really be used when saying something like « rather slow » as a « pre-adjective » or you need to have a secondary aspect but that’s for subject « he’d rather run instead of walk »

.However, alongside the glacier melting, more land and new nautical routes will be discovered, which will/could bring a potential huge fortune in/for these new areas.

Missed a period but who cares. Honestly pretty fantastic the only possible line is « will » to « « could » because we are talking about hypotheticals but still fine to use will and the « in » to « for » this is mainly because money is « in » a object(ie. Money in rocks, in shipping, in farming , money is « for » subjects ( money for the country, brother, sister)

Apologies if I have it mixed but I believe this applies to the grammatical definitions for object and subject in English

It's probably one of the key reasons that (the) American President Trump is seeking the realm/ regions of Canada and Greenland.

Great sentence here some small issues though, we generally say «  the » before titles individuals but it’s actually perfectly fine to not say it and even some new networks will say it « French President » or other countries

And the second is the use of realm I do believe it’s actually 100% correct to use it like this but realm is generally used as a means to make an area seem very different from another

« Going into the eastern realm » when talking about western countries talking to the east and using « realm » instead of « region » to make it sound like it’s a completely different word

Realm in English and literature is commonly used to present an entire new dimension or world which is different. Region is a bit better as highlighting Greenland as a different « realm » isn’t necessary as it’s about geography not foreign culture

It has been known that this is, rather than a simple weather change, it's something long-term and progressive and leads to flood, drought and sea level rising in some regions.

There's a lot of lists in here, so I'd maybe even say "progressively leads to flood, drought and sea level rising in some regions.". It changes the meaning slightly, but helps to get rid of one of the "ands".
It's a sentence that would be more natural when spoken than written.
I put a comma before "rather than a simple weather change" because it's an "aside" - the sentence could exist without saying "rather than a simple weather change", but it adds more information. Putting commas around an "aside" makes it clear that it's an extra thought.