In this post we’ll discuss worldbuilding Oceanic climates, their geography and ecosystems, and reminding ourselves of an iconic Oceanic location that everyone forgets to put on the map.

Hey everyone, my name is Matthew, at least that’s what the weatherman says, and this post is part of a series where I will be going through a science-adjacent worldbuilding process step-by-step. Last time we discussed the dry summered Mediterranean climates, looking at where they’re found across earth-like planets, how to construct a world’s fertile crescent, as well as establishing the flora and fauna that can be found across the dry temperate shrublands.

For today’s discussion, we’ll be discussing our final climate zones among the temperate regions, the perpetually rainy Oceanic climates, sometimes also called Marine climates. We’ll be looking at Oceanic climate zones on earth, before determining how to worldbuild them yourself, as well as how to design some flora and fauna of your own.

Oceanic climates, according to the Koppen climate classification system, are the final climates of this series to fall under the umbrella of temperate climates, meaning that their coldest months have average temperatures between 0 and 18 degrees Celsius, and that they have at least one month with average temperatures above 10 degrees Celsius. Oceanic climates include three distinct climate zones: marine west coast climates, subpolar oceanic climates, and subtropical highland climates.

Marine west coast climates are overwhelmingly the most common oceanic climate type, found most prevalently across the UK, Ireland, the western coastal countries of mainland Europe, and south-eastern Australia. OH! And New Zealand. Almost forgot to put that on the map… As a resident of south-eastern Australia, I’m very familiar with this climate type, which can be categorised as cloudy with a chance of rain in the summer, cloudy with a chance of rain in the winter, and cloudy with a chance of rain everywhere in-between. Marine west coast climates have no dry seasons and warm summers, with all months having average temperatures above 0 but below 22 degrees Celsius, and at least four months with average temperatures above 10 degrees Celsius.

Subpolar oceanic climates, unsurprisingly, are found in more poleward regions, which on earth includes parts of southern Iceland, northern Scotland, eastern Norway, south-eastern Chile, and south-eastern New Zealand, as well as a very thin strip along the southern coast of Alaska. These climates have no dry seasons and cold summers, and all months have average temperatures above 0 degrees Celsius, but only 1-3 months reach average temperatures above 10 degrees Celsius.

Finally, there are the subtropical highland climates, which are rarer climate zones that only form at elevation within the tropics or subtropics. Effectively what is occurring here is that altitude causes oceanic climates to be present in areas that would usually fall into other climate categories. Generally speaking, highland climates found within the tropics will have the same conditions as marine west coast climates, while those found in the subtropics will have dry winters, with higher precipitation in the summer. There is also a fourth oceanic climate type with dry winters and cold summers, found as either monsoon-influenced subpolar oceanic climates, or as cold subtropical highland climates, though this climate type is exceptionally rare and highly localised at altitude. So rare and localised in fact that they don’t even register when looking at a climate map of earth.

Speaking of climate maps, this is the map of Locus, the fictional earth-like planet that we’re creating across this series. As you can see, we’ve filled out our tropical band, and placed our deserts, subtropical and Mediterranean climates. On earth-like planets, Oceanic climates can be found between 45 and 60 degrees north and south, along areas affected by a warm current, which places them immediately poleward of your Mediterranean climates. It can also be presumed that some of the taller mountain ranges in the tropics, and average height mountain ranges in the subtropics, will be host to subtropical highland climates.

If your planet is warmer than earth, Oceanic climates will fall within the same areas but much more confined to the coast, having Mediterranean climates replace them inland, and subpolar oceanic climate coverage will be drastically reduced. Subtropical highland climates would require much higher elevation to form and probably wouldn’t exist within the tropics at all except on the tallest mountains.  

On cooler planets like Locus, Oceanic climates won’t extend as far poleward, giving way to other climates at around 55 degrees north and south, though they would reach far further inland. Which makes Locus end up with an Oceanic distribution of something like… this. Notably, there is a drastic expansion of subtropical highland climates around mountain ranges, with Oceanic coverage extending to average height mountain ranges in the tropics, and just about any mountain ranges in the subtropics.

Now that we’ve placed our Oceanic climates and discussed their geography, let’s look at their native plants and animals. Importantly, the flora and fauna within Oceanic climates differ depending on whether it is a marine west coast climate, subpolar oceanic climate, or subtropical highland climate. For simplicity however, subtropical highland climates are usually home to the same types of creatures as those present within their adjacent tropical and subtropical areas, with individual species having adaptations for cooler weather. And Subpolar oceanic climates are more of a transitionary zone between marine west coast climates and subarctic climates, so it can be expected that flora and fauna there will be a blend between the two. Which only leaves us with the marine west coast climates, which are the most common oceanic climate type anyway.

The consistent rainfall and mild conditions within these marine climates allow for thick dense forests, usually called temperate rainforests, which are found across almost the entire climate zone. The trees within these forests don’t have to worry so much about extreme heat, and the high levels of precipitation make marine climates home to some of the tallest and largest trees on the planet. The most iconic trees in this category on earth are the redwood trees, of which the tallest tree on record, called The Hyperion, reaches 115 meters. For perspective, using the average height of skyscraper floors, the Hyperion would be 38 stories tall. I live close to a temperate rainforest here in south-eastern Australia, and the specific type of eucalyptus trees there can regularly exceed 80 metres tall. What this means is that while there would be a plethora of other vegetation present, the most iconic Oceanic flora will be giant tall evergreens.

On Locus, the Ferracortex are the largest and tallest trees on the planet, growing up to 100 meters. They are evergreen conifers, with phenomenal lifespans able to survive many thousands of years. These traits themselves make forests of them wonderful to behold, though it is an individual family within their order that is the most unique. The Plumacortex have adapted a fictional process called severance, which you can find a video explaining linked in the corner. Specifically, Plumacortex have adapted gravity-severance, which consumes gravitational energy from the area. In functional terms, this means that Plumacortex can artificially remove the effect gravity has on itself, reducing its own weight, and eliminating gravity as a factor for determining its maximum height. This allows Plumacortex to reach utterly incredible sizes, with the tallest specimens reaching up to 1 kilometre in height. The gravity-defying properties specifically come from the sap of Plumacortex, and creatures that ingest the sap are temporarily unbound by the force of gravity, floating until the effect begins to wear off. Of course, the trees themselves are equally as unbound by gravity, and remain tethered to the ground only by their roots. If these roots were to become unearthed, these giant trees would slowly float away, in what can only be described as one of the most comically destructive happenings on the planet. However, the trees’ sap loses its gravity-severing properties after the tree dies, and so a more common occurrence is a dead Plumacortex tree crumbling under its own weight, like a natural skyscraper being demolished. When they are still alive and tethered to the ground, their enormous sizes allow them to dominate their environments, and individual Plumacortex can have entire ecosystems living within them, making them keystone species, and arguably unique environments in their own right. However, very few of these gigantic trees exist due to competition of resources. Though, despite being rare, they certainly aren’t difficult to find.

In contrast with these enormous trees, fauna here in the Oceanic climates tend to be particularly small. However, this may not be due to the climate, but rather due to us as humans. Oceanic climates on earth are mostly present in areas with widespread human settlement. The UK and western Europe for example were once home to a greater number of larger creatures such as wolves and bears, though after a long history of removing larger wildlife, the prevalence of these animals has long since declined.

Most non-European Oceanic coverage on earth exists as subtropical highland areas, with animals there being similar to those from their surrounding climate zones. In fact, the only large-scale marine west coast climate outside of Europe is New Zealand, which is perhaps a poor example of what Oceanic fauna could be like due to it being an isolated island. This triggers a process called Insular Dwarfism, which refers to the condition of large animals evolving a reduced body size when confined to smaller environments such as islands. 

What this all means is that we don’t really have good modern examples of traits that are iconic to the animals within Oceanic climate zones. Modern Oceanic residents are rodents like rats, squirrels, and possums, as well as rabbits, foxes, and deer, none of which are unique to Oceanic climates. As worldbuilders, the most constructive information we have is that the inhabitants of Oceanic climates are mostly either tree-dwelling or burrowing and are probably similar to the creatures that inhabit the surrounding regions. Which isn’t particularly interesting or helpful. However, where we may be able to find our answers regarding unique Oceanic wildlife is in folklore and mythology.

I’ve compiled a chart of iconic mythological creatures from the Oceanic cultures of earth, including Celtic cultures like Welsh, Irish, and Scottish, coastal western European cultures like Belgian and Dutch, as well as the indigenous cultures in Oceania, including Aboriginal Australian and the Māori of New Zealand. While there is a plethora of fascinating and unique creatures across the folklore of these cultures, there is a single type of creature that is consistently present across every Oceanic culture, which is a predatory water dweller that lures people into its body of water. So, creatures like the kelpie, or the bunyip.

On Locus, the Inumbra are heavily inspired by these water dwelling predators and are the apex predators of the marine west coast climates. Visually, they are not dissimilar to real life semi-aquatic creatures like otters and beavers. They are actually a branch of Arborascensus, predominantly tree-dwelling creatures, of which other kinds are abundant among the large trees of the Oceanic climates. The Inumbra however have separated themselves from their evolutionary cousins to fill their own niche, as semi-aquatic predators that ambush creatures from below the water’s surface. They earn their name from their peculiar secondary hunting method, which involves venturing away from bodies of water when it rains or is foggy, using the precipitation to reduce the vision of their prey as well as to mask their scent. Naturally, Inumbra smell of petrichor, which is the earthy scent produced when rain falls on soil, making their scent almost impossible to detect when precipitation occurs. They have exceptional vocal range, using their vocalisations to mimic the sounds of their prey, luring them close before pouncing to attack. In cases of heavy rain or fog, Inumbra can wait until prey is as close as a meter away. If you were to ever find yourself in the dense fog or rain of the temperate rainforests of Locus, an Inumbra could be out of view right in front of you, just waiting for you to take that extra step.

So, to recap, Oceanic climate zones are temperate zones with warm or cold summers, either with no dry season, or dry winters. The exceptional precipitation and cool conditions allow for trees to grow massive, making these climate zones host to some of the tallest trees on the planet. Animals here tend to be small and similar to those from adjacent climates, though a good worldbuilding technique if you are unhappy with real-life inspiration is to turn to the folklore and mythology of the peoples of those regions. If EVERY Oceanic culture has a mythological creature with the same description, maybe that creature actually existed in the distant past, and the tales of water dwelling creatures like Loch Ness may not be so farfetched after all.

Join me next time when we’ll move into the colder subarctic and continental regions, with snow and frost and most importantly, bears! You can find all the information for this video as well as other resources for worldbuilding in general over at worldbuildingcorner.com, and if you enjoyed this video don’t forget to like and subscribe to follow the world-building journey. And until next time… stay awesome!