I created a fantasy map a while back, but only recently have I realised it may have a major problem. There is next to no land at the equator although some land between 0-30 degrees. The vast majority of land that exists is 30 degrees and above. They say Earth's rainforests are the lungs of the world. Have I effectively cut out the lungs of my world and made it less habitable?
Earth's rainforests are definitely not the lungs of world. Actually, they consume all (or most of) the oxygen they produce. The phytoplankton (seaweed and microscopical organisms) are the truly world's lung - if we may say there's such a thing - they are responsible for more than 50% of all the oxygen thrown into the atmosphere.
So, answering your question... you did not necessarily cut off the lungs of your world.
And if I may add some remarks, it is not that simple to define what makes a place less habitable. If you want to think beyond oxygen availability issues, you might think about geography, topology, oceanic currents, air masses, water bodies, atmospheric pressure... there are bunches of things influencing in climate characteristics
Some sources for you to read about oxygen production:
- "How much do oceans add to world’s oxygen?". Earth & Sky. June 8, 2015. Retrieved 2016-04-04.
- John (June 7, 2004). "Source of Half Earth's Oxygen Gets Little Credit". National Geographic News. Retrieved 2016-04-04.
- Biological Sciences: Is the World's Oxygen Supply Threatened? JH Ryther - Nature, 1970 - Springer
- New evidence for enhanced ocean primary production triggered by tropical cyclone I. Lin, W. Timothy Liu, Chun-Chieh Wu, George T. F. Wong, Zhiqiang Che, Wen-Der Liang, Yih Yang and Kon-Kee Liu. Geophysical Research Letters Volume 30, Issue 13, July 2003. doi:10.1029/2003GL017141
Additionally, some sources to read about climate determinants: https://history.aip.org/climate/oceans.htm
As others have stated, your O2 levels should still be OK.
Also, you still may get your rain forests. Look at the coastal regions of Oregon or most of Ireland. They have rain forests and they are nowhere near the equator.
What you need for bio diversity on land would be swamps in warm areas. So of the areas of land nearest the equator (for brevity, here on out, I'll assume Northern hemisphere and Earth's rotational direction; adjust as needed). Also, the southern lands would still get a lot of rain due to wind currents.
With no land in the way, there is nothing to stop the winds along the equator from reaching pretty high speeds. With land masses in the north, the winds there will be slower than the equatorial winds. Streams of air moving at different speeds create eddies in the current where the different streams meet (look at Jupiter's bands for a visible example). I foresee a number of hurricanes being created there. If the southern edge of the land is near that interface zone, it will get a lot of rain.
One effect that I can see is that the poles might be deserts instead of snow fields. Look at the interior of the Antarctic and then go more extreme.
This can be alleviated by having some decent sized seas that extend up north. This will provide atmospheric moisture and a good heat sink to keep everything flowing. You want air in the north to get cold and sink. This will cause the northern air to head south along the surface and allow the moist equatorial air to rise up and head north. Without a significant source of water up north to stay cold, that circulation cycle might stop in the summers as the northern lands warm up. What happens then is beyond my pay grade.
Not necessarily. By definition, Rain forests are forests that get a lot of rain. Consider the Pacific Northwest Rain forest, which runs from northern California into British Columbia and Alaska. Also consider that the Tropical variety. Only Tropical Rain forests occur between the Tropics of Cancer and Capicorn. But other countries have large Rain forests with "Tropical" foliage outside of this region. Japan and New Zealand are practically entirely considered Rain forests despite residing well north or south of the Tropics boundaries respectively. In fact, on our own earth is covered by more temperate rain forests than actual tropical rain forests. Tropical Rain forests do meet an annual rainfall total that is higher than Temperate rain forest rainfall totals.
Conversely, the polar Antarctica is a giant desert. Again, this is because the definition of a desert is characterized by low precipitation, not necessarily heat.
Edit: Useful Note I forgot to add: The Pacific Rain Forest, mentioned above is actually the worlds largest Rainforest, Temperate or Otherwise.
No you haven't made it any less habitable due to low oxygen, remember the Boreal Forests are huge and produce enough oxygen that they create a winter/summer effect on oxygen measurements the world over. Also a large open ocean near the equator will have proportionally larger Phytoplankton Blooms, on Earth such blooms already contribute some 50-85% of our annual oxygen budget.
What will take a huge hit without tropical rainforests is your total species diversity, local diversity of species in tropical rainforests is huge, up to hundreds of species per square metre. Even this is not the issue it sounds like it could be though, the vast majority of those species are found nowhere else on Earth so they have minimal impact on the world as a whole.
Nope, your world is safe. The oxygen in the atmosphere comes from all sorts of sources - trees, grass, phytoplankton and so on. The atmosphere is huge in terms of the tonnes of oxygen it contains. Most of that oxygen is there because of plants which lived and died hundreds of millions of years ago (locking away organic carbon in rocks so it can't decay to CO2), not because of trees which are alive now.
I've heard an analogy for the atmosphere of a full bathtub with a dripping tap. The water is the oxygen. One drip of the tap is the oxygen added to it by all the plants photosynthesising for a whole year. The corresponding one drip spilling down the overflow pipe is all the oxygen removed by respiration (breathing and decay) and combustion (forest fires, car engines) for a whole year.
Also you could compare Earth's rainforests (tropical forests) now, with what they were like at the height of the last ice age: maps of ice age and modern African vegetation zones. The rainforests died back during the various ice ages to tiny remmants and were replaced by savanna, but the amount of oxygen in the atmosphere did not alter.
So if your world is billions of years old, like ours is, it is fine.
I don’t think you would have a problem. The majority of the carbon dioxide absorption / oxygen generation is driven by plankton in the earth’s oceans.
Although a significant part is played by terrestrial plants and animals in our world it will be much less so in your world as (all other things being equal) most of your continents are in the Artic or Antarctic so I would expect just a fringe of boreal forests. However this should not be a problem as there will be both less oxygen production and less carbon dioxide production.
The rain forests are often called the lungs of the world, but this is a misnomer as most of the massive quantities of oxygen produced by them are also consumed by them via animals insects and microflora in various decay processes.
If rain forests really were “the lungs of the world” then we should expect to see a build-up of carbon or carbon rich materials in the forests (CO2 > C + O2), which we don’t generally see. One exception would be a rain forest that was a new growth. Such a system would act as a carbon sink for several hundred years as carbon was locked away in tree trunks. But after the initial growth a steady state would be reached.