In this post we’ll discuss worldbuilding Subarctic climates, their geography and ecosystems, and looking at how plants and animals here have adapted to the harsh cold weather.

Hey everyone, my name is Matthew, at least when I’m not completely frozen over, 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 perpetually rainy Oceanic climates, looking at where they’re found across earth-like planets, as well as establishing the flora and fauna that can be found across the giant damp forests.

For today’s discussion, we’ll be discussing subarctic and continental climates, home to some of the most iconic flora and fauna that are used commonly in fantasy, which we’ll be looking at how to design for your own worldbuilding projects.

Before we can talk about subarctic climates, we first need to understand a concept called Continentality, which is the measure of how much a climate has its temperature moderated by the presence of large bodies of water. Specifically, an area with high continentality will have lower temperature moderation, and some areas with particularly high continentality will have no moderation at all.

Therefore, Continental climates, according to the koppen climate classification system, are climate areas with high levels of continentality, with little to no temperature moderation. They can be found on earth-like planets within the temperate band of large landmasses. On earth, this means that Continental climates are almost exclusively found within the northern hemisphere, as the southern hemisphere has no wide spanning continents within those latitudes. Within the northern hemisphere, a significant portion of Eurasia and North America is host to Continental climates.

Very simply, Continental climates have at least one month with average temperatures above 10 degrees Celsius, and at least one month with average temperatures below 0 degrees Celsius. They follow the same distribution as temperate climates, being split into areas with dry summers, dry winters, and no dry season, as well as areas with hot summers, warm summers, and cold summers. Continental climates also have a further distinction for areas with very cold winters. This leaves us with TWELVE climate types to differentiate between, though we can easily split these twelve climates into two groups; hemiboreal and boreal, which is more commonly referred to as subarctic.

Hemiboreal climates refer to the six Continental climates with hot and warm summers, and function as transitionary climate zones between temperate climates and subarctic climates. Hemiboreal climates with no dry season or dry winters serve as transitionary climates for humid subtropical climates, while those with dry summers are transitionary climates for Mediterranean climates. They have the same temperature requirements as their temperate counterparts, except that the coldest months of these continental variants have average temperatures below 0 degrees Celsius. The geography, as well as the flora and fauna of these climates tend to be a mix between those found in their adjacent temperate zones, and those found within subarctic climates. On earth, hemiboreal climate zones include areas like southern Canada, some northern states of the United States, parts of northern Asia, northern central Europe, southern Russia, and southern Scandinavia.

The remaining six Continental climates with cold summers and very cold winters are considered Subarctic climates and are what we will be focusing on today. While all subarctic climates have 1 to 3 months with average temperatures above 10 degrees Celsius, and at least one month with average temperatures below 0 degrees Celsius, those with very cold winters have their coldest months reach average temperatures below -38 degrees Celsius. On earth, cold summer subarctic areas include places like northern Scandinavia, parts of Russia, parts of southern and central Canada, and a large portion of Alaska. The only place on earth with very cold winter subarctic climates is north-eastern Siberia, and unless your world has an equally wide continent at the same latitude, there may be no very cold winter subarctic climate zones at all. The ’standard’ subarctic climates have no dry seasons, though monsoonal influence can cause dry winters, and Mediterranean influence can cause dry summers. Regardless of their dry season, subarctic climates tend to have relatively little precipitation, though not so little as to be considered arid or semi-arid.

Now that we’ve established what each of the continental climates are like, let’s look at placing them on a map. This is the map of Locus, the fictional world that we’re creating across this series. As you can see, we’ve already filled out our tropical and temperate climates. On earth like planets, subarctic climates start along the polar front and reach as far poleward as 70 degrees north and south, and creep into temperate zones down to around 45 degrees north and south along coasts affected with cold currents. Hemiboreal climates will then fill in any remaining blank spaces in the temperate band which if you have already placed your temperate zones should mostly fall within continental interiors that don’t fall within rain shadows. Subarctic and hemiboreal climates can also be found at altitude, usually on particularly tall mountain ranges within the subtropical regions.

On warm planets, only the tallest mountains in the subtropics would experience continental conditions, and it’s unlikely any mountains in the tropics would at all. On these warmer planets, subarctic climate coverage moves slightly further poleward, sitting between 65 and 75 degrees north and south, and reaching into temperate zones down to around 50 degrees north and south along cold coasts. However, subarctic coverage on warm planets is drastically reduced, giving way to far greater hemiboreal coverage.

The opposite is true on colder planets, like Locus. Subarctic climates expand significantly and will be found further equatorward, sitting between 40 and 65 degrees, angled downwards towards coasts affected by cold currents. Hemiboreal climates then fill the gaps, and their overall coverage is reduced. There would also be a greater prevalence of subarctic and hemiboreal areas along mountain ranges, with many subtropical mountains and even some tropical mountains experiencing continental conditions close to their summits. Which gives Locus a continental climate coverage of something like… this.

Before we move on though, let’s look at this area specifically. On Locus, we’ve marked this area as a cold desert, though it’s important to note that if Locus were to get any warmer, the increase in precipitation would cause the area to become continental. This is the map of the climate zones on earth during our last glacial maximum, and you can see that all of non-coastal Eurasia is either desert or tundra of some kind. North America however is still host to continental climates, though has significantly less continentality compared to Eurasia. Eurasia measures over 11,000kms across, while North America only measures around 4,500kms across, not including Alaska. In addition, Eurasia’s furthest point from the ocean, called the point of inaccessibility, is 2,645kms inland, while In North America, the point of inaccessibility is 1,650kms inland.

Doing some quick behind the scenes math, referring to the information we used when we built Locus, link in the corner, we can determine that the width of this continent on Locus is around 10,000kms from westernmost to easternmost points, with its point of inaccessibility being right here, at about 3,500kms inland. Given that those numbers are closer to those of Eurasia, we’ll keep things similar to what Eurasia was like in the last glacial maximum. I don’t know the exact point between North America’s continentality and Eurasia’s continentality that causes the shift from continental climates to desert climates, but as worldbuilders we can use the information we have here as a reasonable slider between the two. This does however mean that on Locus, areas like this and this are far enough inland to be considered very cold winter subarctic climates and would be some of the coldest places across the entire planet outside of the polar caps.

Now that we’ve placed our subarctic and hemiboreal climates on the map, let’s establish their flora and fauna. As we mentioned earlier, hemiboreal climates serve as transitionary zones between temperate and subarctic climates, so we’ll be focusing on discussing subarctic flora and fauna. Due to the exceptionally cold conditions, moisture in the soil freezes to depths of at least a meter, and the summer warmth is often insufficient for thawing to occur, meaning that most subarctic areas away from the most equatorward regions or oceans are subject to permafrost. This invariably leads to low biodiversity, and on earth only the hardiest of trees can survive the conditions of the subarctic, making subarctic areas almost categorically covered in homogenous forests called Taiga. So prevalent are these taiga forests among subarctic climates that the subarctics are sometimes even referred to as ‘taiga’.

These forests are almost always made up of conifers and are reasonably straightforward to worldbuild due to their low levels of diversity. On earth, the most iconic subarctic confiers are pine, spruce, fir, and larch. As you can see, there are some clearly distinct features present across the board, so we can tell what our trees will likely look like, though these plants also share a less visually obvious feature. Cold Hardening is a physiological and biochemical process that helps organisms prepare for cold weather. Cold Hardening occurs through a process called ‘acclimatisation’, allowing plants capable of cold hardening to steadily develop greater cold resistant as temperatures gradually drop. Acclimatised plants in this way can survive temperatures up to 30 degrees Celsius lower than they would usually be able to, though their growth is effectively halted while this occurs. When temperatures become warmer, the process is reversed, and growth resumes. Without cold hardening, plants would be unable to survive in the subarctic climates, so we can expect that any we worldbuild will be capable of cold hardening as well.

On Locus, the Gelorium are the most common trees found across the subarctic zones and are actually more closely related to grasses like Vell and Siccal than neighbouring trees like Ferracortex. As an Immortalis, they have what is called a phoenix seed, a highly resilient seed designed to grow only after the organism dies. Gelorium’s phoenix seed is exceptionally cold resistant and remains safe underground when winter frosts occur. Uniquely among phoenix seeds, the germination of Gelorium’s seeds don’t only occur when the above-ground organism dies but is also linked to the cold hardening process of the trees themselves. As mature Gelorium trees undergo cold hardening, their trunk hollows out and eventually reach a point of growth stasis where the tree is functionally ‘dead’, triggering seed germination. The seedling will then begin its growth from within their parent tree, effectively cannibalising its parent for nutrients, and using the cold-hardened parent’s body as protection against the frost. With access to an abundance of nutrients from within a safe environment, these young trees emerge from the husks of their parents come spring-time at surprisingly large sizes, making them some of the fastest growing but shortest living trees, and for our future civilisations will make for some of the most abundant and renewable sources of wood on the planet.

Now that we’ve discussed the flora of the subarctic, let’s move on to the fauna present within the area. Creatures present within the subarctic need a means of staying warm, and the easiest means of doing so is to adapt a larger body size. Bergmann’s Rule and Allen’s Rule both detail that a smaller surface area to volume ratio reduces the rate of heat loss for animals, and accurately predict that species living in colder climates grow larger that their relatives in warmer climates. On earth, this can be found across a number of animal types, including bears, deer, cats, wolves, penguins, and rabbits, all of which have the largest species of their type inhabiting the coldest areas on earth, while those living in warmer climates are smaller. Anyone who lives in areas with moose can verify that people are always surprised at just how big they are. What this means as worldbuilders is that while not all creatures of the subarctic will be huge, subarctic inhabitants are likely to be larger than their more equatorward relatives, and some of the biggest creatures on the planet are likely to make the subarctic their home. Importantly, on planets colder than earth like Locus is, the expansion of the subarctic zones will allow for a wide variety of these larger animals, and we can be generous with establishing a ‘large variant’ for most creatures that live here. On warmer planets, subarctic reduction means that fewer of these larger creatures could find a home, and on earth, global warming is sadly causing many of our iconic subarctic animals to become endangered due to habitat loss as our subarctic regions grow smaller.

I’ve been looking forward to worldbuilding an equivalent of a bear for some time, and so on Locus we have the Velatrox, which are the bulkiest members of the Velocauda family, and are not only one of the largest predators on the planet but are also the apex predators of the subarctic climate zones. Like many bears on earth, Velatrox are covered in thick fur to provide protection from the cold and are mostly carnivorous, though have one of the most varied diets among carnivores. They have significant sexual dimorphism, with males being over twice as large as females, having adapted great strength for hunting some of the largest land animals on the planet. Females on the other hand are adapted for fishing and foraging, and communities of Velatrox involve males and females coming together to share food. These communities are led by females, who enjoy a more stationary lifestyle living along rivers where fish and foliage are more plentiful. The numbers of these communities are greatly influenced by how much food is available. In areas where food and resources are abundant, Velatrox can settle in almost permanently, with some river camps hosting many generations, with males travelling great distances to trade food and favours with the successful females of the area. The offspring of these males then enjoy access to more plentiful food and communal learning, and so natural selection would favour males who spend more time hunting for a community rather than for themselves. Provided resources remained abundant, this would create a snowball effect with every subsequent generation that has access to these settlements becoming stronger and smarter, allowing Velatrox a position as contenders for creatures that may go on to develop intelligence and civilisations of their own.

So, to recap, the subarctic regions are the final frontier before the polar regions on earth-like planets, and are categorically forested with homogenous flora, though are home to a number of animals that grow larger than their more equatorward counterparts. Both plants and animals here must be able to survive the blisteringly cold winters and have adaptations to allow access to resources more easily.

Join me next time when we’ll discuss our final climate zone within the koppen classification system, the polar climate! 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!