In this post we’ll discuss worldbuilding Mediterranean climates and fertile crescents, where they’re found, their flora and fauna, and most importantly, why they’re integral for developing civilisations.

Hey everyone, my name is Matthew, at least during monsoonal irrigation, 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 subtropical climates, looking at where they’re found across earth-like planets, as well as establishing the flora and fauna that thrive within the swamps and marshes that dominate the humid regions.

For today’s discussion, we’ll be moving across to the other side of the temperate band to the iconic Mediterranean climates, with fair weather, dry summers and fertile conditions that provide the foundations for some of the most important ecosystems on the planet AND are the locations of the some of the most successful early empires in history.

Mediterranean climates, according to the Koppen climate classification system, 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. Mediterranean climates include all temperate climates with a dry summer, creatively named the hot-summer, warm-summer, and cold-summer Mediterranean climates. Hot summer Mediterranean climates have at least one month with average temperatures above 22 degrees Celsius, warm summer Mediterranean climates have no months with average temperatures above 22 degrees Celsius, and cold summer Mediterranean climates have less than four months with average temperatures above 10 degrees Celsius. Notably on earth, cold summer Mediterranean climates are exceptionally rare, and only really occur at high altitude.

Mediterranean climates, shockingly, are named after the iconic Mediterranean basin, which is the most common location on earth for these climate types, though Mediterranean climates can also be found along the western coast of other continents, such as the state of California, southwestern South Africa, and south and southwestern Australia. These climates are commonly covered in shrubland and woodland, with vegetation that has adapted to survive periods of drought during the dry summers. Because of this, Mediterranean climates are home to many annual plants, making them excellent sources of hardy grains that grow consistently, and so are perfect environments for agriculture. Also, as the Mediterranean’s dry season coincides with warmer weather, wildfires can spread throughout the region in summer, though are not as common as in the savanna regions.

This is the map of Locus, the fictional earth-like planet that we’re creating across this series. As you can see, we’ve already placed our tropics, deserts, and subtropical regions on the map. Mediterranean climates can be found on earth-like planets between 30 and 45 degrees north and south, along areas that are affected by a cold ocean current. If your ocean currents are the same as earth, like Locus’ are, then your Mediterranean climates should not only form on the western side of your continents but will be on the opposite sides compared to Humid subtropical climates.

If your planet is warmer than earth, then Mediterranean climate coverage expands drastically. Not only can they be found between 30 and 45 degrees along areas with cold ocean currents, but they can also be found between 45 and 60 degrees, along areas with warm currents, replacing much of the oceanic climate zones in the area. As a warmer planet, it can be expected that Mediterranean climates would trend more towards hot summer climates, compared to warm and cold summer ones, especially in more equatorward regions. If your planet is cooler than earth, like Locus is, then there will be an expansion of Mediterranean climates as they reach further inland, but otherwise, they’ll still only form in areas between 30 and 45 degrees affected by cold currents. So, on Locus we have a coverage of something like… this. As a cooler planet, it is likely that Mediterranean climates here would trend more towards the warm and cold summer variations, rather than hot summer ones.

When it comes to worldbuilding, Mediterranean climates play a crucial role when it comes to developing civilisations, as they provide the most optimal conditions for the establishment of agriculture. The weather across Mediterranean climates is generally fair, with consistent seasonality. Most non-tree flora within the Mediterranean are annuals, meaning that they complete their entire growth cycle within a single growing season, and then die. Almost all vegetables and crops that most people are commonly familiar with are annuals, including rice, wheat, corn, lettuce, beans, and peas. Natural selection within Mediterranean climates strongly favours plants that are annuals, able to complete their entire growth cycle before the summer droughts.

In addition, annuals specifically within the Mediterranean climate tend to be especially hardy, growing throughout the winter. This hardiness combined with their consistent seasonality makes Mediterranean annuals likely to be some of the first plants that are farmed by early civilisations. Where this process is turned up to 11 however is in areas like the Fertile Crescent, which is a crescent shaped area that starts in northern Egypt, moves up through to parts of Turkey, before coming back south through to Kuwait. These areas, already experiencing generally fair weather, received regularly occurring natural irrigation from the Nile, Tigris, and Euphrates rivers, which provided exceptionally rich soils and hydration. The Nile floods annually due to monsoonal activity in summer, while the Tigris and Euphrates flood annually in the spring due to snow melt from the nearby mountains. This doubling up of climate conditions favouring annuals, and consistent annual irrigation, meant that crops within the area had some of the most fertile conditions across the planet.

What this means as worldbuilders is that any Mediterranean regions that flank a river connecting to a bay, or rivers that have runoff from nearby snowy mountains will be prime conditions to create your world’s own cradle of civilisation. On Locus, we have two locations that fit these conditions, one on each continent, both in the southern hemisphere, which we’ll almost certainly be revisiting when it comes time to establish our civilisations. For now though, let’s build the hardy annuals that will be found commonly within the regions.

The Siccalbum, or Siccal Grass, is the most widespread and successful annual across the Mediterranean climates on Locus. It is a cereal grain that has become widespread due to its non-fussy growing conditions, cold tolerance, and resistance to disease. It gets its name from its signature white stalk heads that feel dry to the touch, keeping moisture safely locked inside its stalk. It’s considered a ‘winter crop’, meaning that its growing season starts in autumn and concludes in spring before the grass dies in summer. Like Siccal Grass’ cousin Vell Grass from the savanna, it has what is called a ‘phoenix seed’, a highly resilient seed designed to grow only after the organism dies. Siccal grass’ phoenix seed germination however isn’t triggered by fire, nor by weather, as temperatures between summer and autumn in the Mediterranean are not too dissimilar. Instead, the seeds have photoreceptors that determine once the autumnal equinox is reached, meaning that nights are at least as long as days and getting longer, which on Locus is 10 hours of daylight or less. No matter their latitudinal location, regions across the Mediterranean would reach equinox within just a few days each other, meaning that Siccal Grass sprouts across an entire hemisphere almost simultaneously as soon as equinox occurs. Siccal Grass will therefore likely be an excellent marker for civilisations as they develop calendars of their own.

As mentioned earlier, Mediterranean climates also tend to be covered in shrubs and bushes, and on earth the most distinctive Mediterranean flora are called Sclerophyll, which refers to a type of vegetation that has adapted to long periods of dry conditions, such as the droughts that are common throughout the Mediterranean summers. Sclerophylls have leaves that are hard, grow parallel to the sun, and have short distances between leaves when compared to other plants. Some of the most iconic Sclerophylls are trees such as the olive tree and eucalyptus tree, as well as shrubs like rosemary, thyme, and lavender.

On Locus, there would be several Sclerophylls that are found throughout the Mediterranean regions, though perhaps more interesting than the shrubs and bushes themselves are the main force that threatens them. This threat is not a creature, nor fire nor weather, but rather a type of Pilea, the analogue for fungi on Locus. Malaurum is a parasitic organism that grows on the roots and lower trunks of the shrubs and trees here. It is capable of a fictional process called arcanosynthesis, which you can find a video explaining in the corner. Put simply though, this process allows Malaurm to create its own energy, which it stores in tubers that look like golden coloured truffles. Excess energy is then used to produce a growth hormone, which is highly mutagenic. Malaurm doesn’t use this growth mutagen on itself however, but rather infects its host with it, causing the tree or shrub to regenerate and mutate as it continues to be eaten by the Malaurum. Infected florae are then totally at the mercy of the random ongoing mutations that they are subjected to. If a creature eats the fruit of an infected tree, or the tuber of the Malaurum itself, it’s possible for the creature to become infected and subject to mutations themselves. Notably, this mutagen breaks down at high temperatures, and if the golden tubers were to be cooked appropriately, they could be a safe highly nutritious food source. While not particularly relevant to our current non-fire wielding creatures, stay tuned for these tubers to become incredibly important in the future.

In the meantime however, Malaurum’s mutagen is responsible for the creation of a very unique type of creature that has come about as a result of mutation. The Decemora is a predator, heavily inspired by the hydra from Greek mythology. For better or for worse, they have mutated a reduction in the proofreading that their DNA polymerases undergo during DNA replication. What this means functionally is that they have mutated an increase chance of mutating. This, combined with repeated exposure to the mutagens of the Malaurum has drastically distanced Decemora from their evolutionary cousins. Their most notable feature, for which they get their name, is a trait called polycephaly, which is the condition where a creature has more than a single head. On earth, not only are there instances of polycephaly, but even instances of polycephalous creatures that have been able to successfully reproduce. Decemora originally reproduced sexually, though their high mutation rate has made viable offspring borderline impossible. Their critically endangered lineage now exists solely as descendants of a singular Decemora that evolved the means of asexually reproducing through Parthenogenesis, meaning that eggs laid are functionally clones of their mother at the time of laying. The species’ inherent ability to mutate non-sexually often means that by the time eggs hatch, their mothers are so different from their offspring that they could no longer even be considered related.

Decemora are birthed with two heads, sharing a circulatory system, and they have evolved to instinctively bite off any head that dies to avoid sepsis. However, their notable mutations have also granted them limb regeneration, similar to lobsters on earth. This process is slow, and very energy intense, but given sufficient calorie intake, a Decemora can regrow up to three heads from its original stump. To fuel the calories needed for this process Decemora will often continue to feed on the energy rich Malaurum, which causes even further mutations. This leads to multi-headed Decemora being truly bizarre creatures, with variations in their biology too numerous to appropriately list. However, in most circumstances, mutations are detrimental, and Decemora that aren’t outright killed by their mutations live pained existences, and while evolution unchained is a truly fascinating concept, the reality is that Decemora are far too unstable to ever reach high population numbers and are rapidly driving themselves towards extinction.

So, to recap, Mediterranean climates are temperate zones with dry summers, split into hot, warm and cool variations. The drought risk makes the area unsuitable for most trees, instead giving way to shrubland that is better suited for lengthy dry conditions. Mediterranean zones with access to regular natural irrigation are some of the most fertile areas on the planet, making perfect areas for civilisations to be birthed.

Join me next time when we’ll finish up with our temperate climates, discussing the cooler and rainy oceanic climates. You can find all the information for this video and 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!