In accommodation to my last question, we are now transferring from meteorology to ecology.

Today, tropical rainforests take up only 3% of the world's surface, yet they take up half of the plant and animal species (that we know of--if Blue Planet II were to be taken into consideration, it's that deep-sea habitats are not as barren as once thought.)

During the Eocene epoch, such habitats had filled up all of the Earth's continents. Today, half of the world's species varies in translation between three and 50 million species. Now, in an alternate Earth where the 21st century in the Common Era is as hot as it was 50 million years ago, what would happen to those 50 million species? Would they multiply into a higher number of new species? Or would the global jungle give those original 50 million more territory to claim?

  • $\begingroup$ Can you talk about the landmass on this planet - where it is on the globe, and how large it is? $\endgroup$
    – HDE 226868
    May 16 '18 at 14:45
  • $\begingroup$ Answer depends only on two conditions: Will your jungle create more ecological niches? Would it inhibit travel and thus gene mixing enough? If yes, then more species. If no, more territory. We can't know from your question which one would it be. $\endgroup$
    – Mołot
    May 16 '18 at 14:45
  • $\begingroup$ "...varies in translation.."? what are you trying to say? $\endgroup$ May 16 '18 at 17:47
  • $\begingroup$ Evidence for the claim that tropical rainforests had filled up all the continents? Seems unlikely, since rainfall is strongly determined by geographic features such as the rain shadow effect of mountain ranges. $\endgroup$
    – jamesqf
    May 16 '18 at 18:29
  • $\begingroup$ @EveryBitHelps rainforests.mongabay.com/0301.htm $\endgroup$ May 16 '18 at 20:44

Species tend to fall in rapid changes, and rise within evolutionary niches

The study of speciation is a major field of study - indeed it has occupied many palaeontologists especially regarding the rate of speciation or extinction.

It is generally accepted that several factors affect the number of species over time and a sudden change of environmental conditions, green or not, may indeed initially reduce the number of species dramatically as in extinction events or quick geological changes, as species struggle to adapt to new conditions (imagine desert species, grasses, insects and plants that were adapted to arid, dry or even temperate environments) and become endangered or extinct instead.

Over time though it is theorised speciation occurs most within evolutionary niches. A large stable environment is actually theorised to prevent speciation, as species tend to only separate in small, stressful or isolated populations.

So to answer the question, yes there will be change and the number of species will likely fall more than rise in a sudden alteration of the environment.

Over time though it would, through evolutionary niches (in which there are many in jungle environments) increase steadily, and there is no reason to think it wouldn't be as varied as the great continental jungles were in the past.

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    $\begingroup$ I don't think the OP intended a sudden shift from current climate to new jungle climate. Just that the jungle climate stayed in existence until now. $\endgroup$ May 16 '18 at 15:19

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