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I am wondering about this map, from the game Albion (not Albion Online): enter image description here The island on the right (Umajo) is an arid one, mostly covered by sandy deserts, except for an area of savannahs at the very south (not pictured in this map). The other islands are either completely covered by tropical forests (i.e. the ones on the bottom and left-bottom). The rest is temperate climate/forests type, except for the peninsula in the middle of the image, under Beloveno, where jungles start to prevail. It mostly matches the northern hemisphere of Earth, except for the arctic and subarctic areas.

Now it seems weird to me that deserts formed on that island, though it's larger than the other islands (but the deserts span from coast to coast). I assume that the map uses the usual directions (right is east, top is north), thus the island lies in both the temperate and tropical zone, so it should be more akin to the other islands lying there. So my question is - what natural process could cause the formation of deserts on the island (and also the hot climate present there).

From what I know about this world, it is located in the same universe as the Earth, so same physics should apply. However, magic is also possible on Albion, but I'd rather look for a natural cause.

We also know that the planet has gravity about 0.8 G, and no axial tilt, leading to the complete absence of seasons on the planet. The revolution time is the same as Earth's, so it has the same length of the day and year. The atmosphere is also quite cloudy, but from from I observe from other artworks, the sky above Umajo is clear and cloudless. That may be the cause (or the effect?).

Edit: As human activity can be a factor in this, I have to clarify more about the population. The humans that live in this world are the descendants of the Celts originally having come from Earth ca 2000 years ago, and therefore I suspect that it's unlikely that deforestation created the desert. The other (and original) inhabitants of the world live in great harmony with the nature, and wouldn't willingly cause any deforestation in that area.

The age of the game also makes it a bit harder to express the exact relief of the island, but aside from a mountain/boulder ridge in the central area, the island is mostly flat.

To illustrate the nature of the island, here are some images: enter image description here enter image description here

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  • $\begingroup$ Your question is not about world building. Your world is already complete, and you are asking us why there is a specific terrain in your world. It is your job to justify why and how that happens in the first place. $\endgroup$ – Vylix Aug 25 '17 at 3:25
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    $\begingroup$ @Vylix that is a perfectly acceptable use of WB'ing $\endgroup$ – James Aug 25 '17 at 5:12
  • $\begingroup$ Simple answer is that natural causes wouldn't allow the whole island (continent?) to be desert. (Assuming, as you say, that the map covers northern hemisphere from tropics to temperate regions.) Look at a map of Earth: deserts are either at particular latitudes, or they are in the rain shadow of substantial mountains, which the island doesn't seem to have. You might reasonably expect a band of desert around mid-latitudes (like around the Mediterranean), but the north should be rather European, and the south fairly tropical. $\endgroup$ – jamesqf Aug 26 '17 at 5:27
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    $\begingroup$ Why is this off-topic? I am looking to extend the history of the world by finding a physically or geographically accurate explanation of a placement of a desert. Whether it is or is not possible is the domain of the answers. $\endgroup$ – IllidanS4 Aug 26 '17 at 11:59
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Jet Stream

Draw the jetstream in this world around that island such that it does not experience substantial rain.

Cliff Faces

If the side of the island that faces the incoming jet stream or "prevailing westerlies" type of winds has high mountains or cliff faces, the weater will drop rain right there or it will slide around the island.

Volcanic

If the island is principally volcanic in nature, the soil is rocky sand rather than smooth sediment and will both absorb heat more and fail to capture any but the hardiest of plants.

At the end of the day, admit to its creation

You need to realize that the creators of the game most likely created the map with no intent of being geologically or meteorologically correct. It's fun to speculate as to how it might be, but imposing rules and governance on a creation that's 100% fiction is almost always unsatisfying. Consider my answer about plate tectonics in Tolkien's Middle Earth where someone wanted to know what the in-universe explanation was. Most of the time, the answer is, "well, I made it that way."

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  • $\begingroup$ I edited to clarify more the shape of the island, but nice idea about the jet stream. The sand appears smooth, with dunes, and there is still some little vegetation after all near the river and the south. I get that the creators payed little attention to science when creating the world, but it's still fun to speculate. Also Albion is partly sci-fi (the Toronto located in the middle of the island is actually a recently arrived spaceship). $\endgroup$ – IllidanS4 Aug 25 '17 at 0:24
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Just model it after Socotra in Yemen minus Socotra's mountains. It is a world heritage site. http://whc.unesco.org/en/list/1263

The island has a tropical desert climate, except for the mountain region that gets a bit more rain. The mountains get more rain because the mountains force warm air upwards where it expands and cools. Relative humidity compares the vapor pressure of water to the water content of particular air. The vapor pressure decreases with decreasing temperature, boosting the relative humidity in the process. Rain occurs if the relative humidity passes 100%.
https://en.wikipedia.org/wiki/Socotra#Geography_and_climate

The converse must also be true. Vapor pressure increases with increasing temperature, lowering the relative humidity in the process.

As an added bonus, Socotra comes with unique species like the Dragon's blood tree to help you populate the landscape. https://earthobservatory.nasa.gov/IOTD/view.php?id=78411

Socotra is generally dry because it does not get monsoons. It does not get monsoons because the water is generally colder than other areas of the same ocean basin. The cold water comes from upwelling from the deep. https://charliesweatherforecasts.blogspot.com/2015/11/why-did-yemen-and-socotra-just-get-hit.html

The combo of hot air (boosting the amount of water needed to reach 100% humidity) and cold water (lowers the rate of evaporation) leads to air that is very dry even though it is above the ocean. Monsoons do not like dry air. You end up with wind but no moisture. Finally, make the island entirely flat, and you are good to go.

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    $\begingroup$ That is a lot of nice resources, but please refrain from sending people away by simply posting links. If linked resources change or removed, your answer will be invalidated and might be deleted. Give us the essential parts why you think these resources may answer the OP's problem. $\endgroup$ – Vylix Aug 25 '17 at 5:49
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    $\begingroup$ welcome to WorldBuilding! Please always summarize the most important things from the resources you link. Links can get outdated, which would leave your answer pretty much useless for future readers. This answer is currently in the low quality review queue because it is what is often called a "linik-only answer". Please edit it to write some summaries. Otherwise this answer might get deleted. Have fun! $\endgroup$ – Secespitus Aug 25 '17 at 6:28
  • $\begingroup$ I did fix it. I won't be answering again though any time in the future. Posting on this site is just unpleasant. Much as I understand why you don't like links, most of the other answers did not even try to look for real world examples despite the ease of doing so. $\endgroup$ – emawerna Aug 26 '17 at 4:08
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Take a look at earth deserts, e.g. the Sahara, some of them border oceans and other bodies of water and still are mostly sand/deserty-stuff.

As long as there's an absence of any precipitation there won't be much growing. Clouds need a motivator to make it rain. Most often this motivator is either mountains or too much water in the air. If you get rid of both you don't get much rain.

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    $\begingroup$ The sahara was largely caused by massive over farming with little to no rest periods for the soil. Overuse of an area for long periods would cause soil to become depleted and wash away with the rains. As that process becomes more exaggerated you'll get a cycle of desertification as plants die from lack off nutrients. Couple that with lack of rains from loss of evapotranspiration and over decades and centuries you have a desert. $\endgroup$ – Casey B. Aug 24 '17 at 23:48
  • $\begingroup$ Well, there are those savannahs in the south, and there is also a mountain ridge in the center of the island, but far from the south. $\endgroup$ – IllidanS4 Aug 25 '17 at 0:15
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As a reference (less extreme, but...) you can look at two largish and very similar islands in Mediterranean: Sardinia and Corse.

Sardinia is not desert, but very arid, while corse had large and high forests.

Both climate and geology is similar. What happened?

Man happened. Both islands were covered by forests but, while Corse was not meddled too much, Sardinia forest were burned down to make pasture for sheep and goats.

This changed completely climate because while in Corse land is colder then sea (due to forests) in Sardinia land is much hotter than surrounding sea.

This fact inverts prevalent air circulation and while in Corse sea humidity rises and is sucked down over land, raining on it, in Sardinia you have the reverse: normal circulation is hot air rising on land taking with it the scant humidity present and then going to discharge rain on sea.

To have an island with desert climate is enough to cut all (or good part) of forests on it; if there is enough sunshine it will do the rest of transformation.

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  • $\begingroup$ Good point, but I think it unlikely for men to have caused this. See the edit. $\endgroup$ – IllidanS4 Aug 25 '17 at 0:25
  • $\begingroup$ @IllidanS4: the whole point is not if deforestation is man-mad or not, point is when vegetation lessen, at a certain point air circulation inverts and rainforest switches to desert (this is what we currently risk in Amazonas). Initial forest dwindling can be for any reason, including a large fire or something similar; after a certain trigger point phenomenon is self-sustaining. $\endgroup$ – ZioByte Aug 25 '17 at 0:38
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I believe the most common cause of dessert on earth is humans. The process is actually called desertification. It usually involved deforestation, poor farming practices, poisoning the ground, and a natural tendancy to low precipitation.

However you state that this is a land that is "one" with nature.

Option #1. Past

Perhaps the people are one with nature because of what they did to this island.

Option #2 Cataclysmic force.

An earthquake, meteor, tsunami, volcanic eruption, or magical beast could have caused this.

Option #3 End of the world.

I think the sun is actually supposed to get colder as it gets older but a decaying orbit might draw the planet closer to the sun. This would result in storms, heat waves, unpredictable weather and general chaos. Wouldn't likely spare the other islands though.

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