# Can a small island realistically have all these environments?

Would it be realistic for a (relatively) small island nation to have these features:

• A Forest

• A lake

• A snowy mountaintop

• A desert

• A bustling modern city

How large would this island have to be in order to have all these enviornments?

I am imagining this island to be not far off the East coast of North America, but its exact latitude is flexible. The nation was mostly settled by European explorers in colonial times, but is now an independent country. Its main exports are technology.

• Asking too many sub-questions in one post will get a question closed as too broad. I removed most of the secondary questions to focus on the primary one. After getting answers here, you can post followup questions separately. Welcome to Worldbuilding. Mar 13, 2017 at 17:40
• How small is realitively small? 1 x 1 mile? 10 x 10 miles? 100 x 100 miles? Given that many people are surprised at how small Ireland is (approx 300x170 miles), is Ireland a small or relatively small island? Mar 13, 2017 at 17:45
• Also . . . how big does your lake need to be? 100 meters? 1 mile? 10 miles? If you get the minimum size of the items you need, then you're on the way to having the minimum size of the island. Without those criteria I can't help you. Mar 13, 2017 at 17:47
• Giving this a -1 for lack of research and vagueness. Mar 13, 2017 at 17:57
• Welcome to the site Jayen. Check out the help center when you have a chance to get some guidance on writing good questions and answers for the site. For this question I would recommend providing your goal with some specific details, maybe mention that you want to be able to traverse the island in a day with modern tech to establish what size you are looking for, just an example. As it stands we don't know enough detail about your goal to help you get there. Mar 13, 2017 at 18:44

# Forests and deserts

Forests an be pretty much anywhere; there are lots of different types of forests. Having a forest and desert on the same island is pretty easy too. The island of Madiera (in the Atlantic) has a semi-arid southern coast, and a wet forested northern coast.

The key to this wet/dry divide is for the island to be in a cold current around 30 degrees north or south. Prevailing winds hit the one side of the island and deposit moisture, while the cold current reduces cloud formation over the dry side of the island. The Hadley cell providing dry descending air will complete the picture. Madiera is only 801 km$^2$, about the size of Singapore, so this effect can be prominent in a dry island. There isn't a cold current off the coast of the Eastern US, you can see here, but such an island could exist off Western Australia, Baja California, Peru, Angola, or Morocco (which is where Madiera is).

# Cities

Cities can go pretty much anywhere, and are pretty straightforward. You can look up city sizes on Wikipedia to see how big a city will be for a given population.

# Snowy mountain

The moist adiabatic lapse rate is the rate at which temperature drops off with altitude and is about 5C / km. If we take Madiera as an example, the capital (Funchal) has sufficient winter moisture for snow, and just needs to be colder. Since the daily mean is about 16.7C, we'd need to drop that by about 15-20 C to see regular snowfall on the top in winter. That means we are looking for mountains in the 3-4km range. This makes sense, since Mauna Loa and Mauna Kea at around 4205 m have snow on their summits a few degrees farther south on Hawaii Island.

The smallest island with a 4km mountain is that same Hawaii, at 10430 km$^2$. Going down the list, there are several that have a 3km peak while being only about 2000 km$^2$; Bioko, Siple, Tenerife, Reunion, and Ross Island. So we could expect a 2000 km$^2$ island to be able to support a snowy mountain.

# Lake

What sort of lake do you want? The easiest way to do this is with a crater lake. For example Lombok has a 3700m mountain with a sizable crater lake on top of it. Lombok is about 4000 km$^2$, but any of those other islands with a comparable volcano could have a similar lake.

# Conclusion

Your island must be at a minimum 2000 km$^2$, which is around the size of Maui, or a little more than half of Long Island. This leaves about 1/3 of the island to be covered in a city-state the size of Singapore, 1/3 to be covered in desert and forest, and the last 1/3 to be the steep slopes and summit of a mighty volcano, topped by a crater lake.

Come to New Zealand



Waipoua Forest



Lake Tapo



Mount Cook



Rangipo Desert



Wellington



Here is a picture of how close together all the natural features can be. Note not all the examples above and below match. But here we see Rangipo (1), Lake Tapo (2), Mount Ngaurhoe(3) and the Kaimanawa Forest Park (4) all within about a 50km range. There is no reason a city couldn't be built within that reach.

• Interesting answer, but could you provide more information regarding the question? "How large would this island have to be in order to have all these enviornments?" Mar 23, 2017 at 14:18
• You could conceivably do it within 2500 square kilometres of island. Mar 23, 2017 at 15:01

Examples abound. If we loosen up the requirements a bit for multiple environments, all that you need is an island with a decent mountain range, in a location with a strongly prevailing wind. The Olympic peninsula in Washington State is a rain forest on one side, and about 13 inches of rain a year -- not quite desert, but all the farming uses irrigation. A thousand feet higher would do it.

Vancouver Island is another example.

Note that a single peak will likely not cast enough of a rain shadow. Prevailing winds do have some variation.