Borneo's forest look

Normally, it need to know the life cycle of different trees and other plants.

If it is the some or not in the time. You can test the âge of fall trees, etc

Animal reduced is only one of problems...

Dest regards,

Marpha

Actually, the demographic history may be reconstructed for selected species by exploring the genetic diversity distribution among individuals across Borneo's forests. Using genetic markers such as SNPs combined with coalescence modelling (ABC model), you may be able to trace expansion and shrinkage of populations through time as predicted by your scenario for changes in forest structure.

Hi

there are two different questions, the one in the tittle and the one at the end. Even with no activity of large mammals, as suggested, a wet tropic forest is always submitted to partial rejuvenation by "windfalls" (trees which fall down for various reasons) and thus rapid backward structural evolution followed by slow forward reforestation. This is for tittle question. Then for the second question, testing the diversity of pionneer species is indeed a possibility. The share of the different types of seed dispersion (anemochorous, endozzochorous, etc.) could also be a possibility.

regards

Hi Erik. Not sure if I can tell you anything you don’t know already, but I can share some thoughts.

There are various issues to consider. The climate then and now. The direct effects of humans (mainly modification of vegetation through fire, modification of the fauna through hunting) and the many resulting consequences including the indirect effects and interactions.

Climate:

If 70,000 years ago is the reference (let's initially ignore the foonote on what the 19th century explorers might have seen) this lies within the last glacial period when the Earth was generally cooler and drier, so global vegetation was generally not comparable with what we see now (even without global warming, we live in an interglacial which means the conditions are far from typical of those that have prevailed for the last two and half million years, when glacials were the norm). Nonetheless there is evidence to suggest that wet tropical forests persisted in Borneo (which was joined to Asia due to the lowered sea level through most of the period). There were drier vegetation types (woodlands and open savanna), see the studies by Chris Hunt and others for the various evidence ( https://www.researchgate.net/profile/Chris_Hunt6 ).

By the time the 19th century explorers arrived it was much warmer and wetter.

Human actions:

Humans likely burned local areas of forest when they arrived generating at least local open areas (data from Niah Cave etc). This likely increased the abundance of fast breeding ungulates (and other species) that can use these habitats. Large scale rice agriculture in the interior of Borneo is also something relatively modern as it required iron tools (starting a millennia ago and incomplete even by the colonial era in Malaysia and Indonesia (I briefly reviewed in my co-authored article: https://www.researchgate.net/publication/244988296_2012_Do_Anthropogenic_Dark_Earths_Occur_in_the_Interior_of_Borneo_Some_Initial_Observations_from_East_Kalimantan )

Some animal species, especially larger species, have been much reduced by hunting. The main declines have been recent (mainly over the last couple of centuries). Richard Corlett made a useful summary of evidence on these patterns in the wider region (see https://www.researchgate.net/publication/227941800_The_Impact_of_Hunting_on_the_Mammalian_Fauna_of_Tropical_Asian_Forests?_sg=lBQPCekNVJTRHi97MMG2roeGxjd889AAMBmvIh7Zj5la8XpzKyozjrn9-e9ZK6338LVEmAsLilxYEg.k9vXh5YfaI3sRs8ehuf2qCcYCkhujn6fIoPVA6VCVHzFkjTq8RDpSCb71BXuarv7fNCdKQxHzIlmClup7DLFJQ&_iepl%5BviewId%5D=1cZjxbqt90Cq4f7Q4QDD6AQ7&_iepl%5BprofilePublicationItemVariant%5D=default&_iepl%5Bcontexts%5D%5B0%5D=prfpi&_iepl%5BtargetEntityId%5D=PB%3A227941800&_iepl%5BinteractionType%5D=publicationTitle). These events were ongoing since before the 19th century explorers arrived (and have increased since).

Implications of animal loss:

The loss of large animals can results in a variety of impacts. Loss of larger carnivores can result in increased densities of prey species (with impacts for the species that these feed on and disperse). Loss of large herbivores will generally lead to less major disturbances related to these animals (this can result in a denser understorey ... with whatever knock on effects this may have). My own work in Africa suggests that the loss of elephants is associated with denser rain forests with more small plants persisting, but also suggests that some plant species benefit from the loss while others lose (it is complex as some species may be preferentially eaten but still benefit from the disturbance caused) ... see https://www.researchgate.net/publication/227728649_Forest_Tree_Persistence_Elephants_and_Stem_Scars . The influence on other animals are also nuanced and can go either way depending on conditions ... there may be some release of competing species or a negative impact on species that depend on them (these large animals often they help maintain forest clearings, or slow their recovery, they may also maintain areas as grazing areas ... and influence flammability etc). A particular interest in Borneo is the loss of the animals that generate wallows (mostly rhinos I think) though they may be maintained by pigs (??? Anyone know). The general conclusion is that the consequences of large animal reduction are complex and likely influence the entire forest community. The general outcome of the shifting fauna is that forest regeneration, composition and structure will all be modified. The nature and degree of these changes in uncertain (we lack good data on selective effects, and even on the pre-human animal densities that might allow us to estimate these impacts, though I think I saw at least one good overview by Liz Bennet, I looked but cannot find it now ... https://www.researchgate.net/profile/Elizabeth_Bennett7 ). The various reviews on "Empty Forests" by Redford and subsequently but others have generally neglected Asia but they do identify a range of possible impacts too that may be worth a look at (for example loss of seed dispersers etc). The major disruptions in pig migrations in recent times may also be a major impact in the long term given that so many tree species in Borneo seem adapted to avoid seed predation by these animals (see e.g. Lisa Curran's articles).

Putting it all together:

70,000 years ago it was drier, cooler and more open. Borneo was part of mainland Asia. There were more large animals than now. When people arrived there was an increase in fires, and maybe some local declines in larger animals (and maybe some increase in others). These declines became extreme in the last century and have likely led to shifts in forest regeneration, composition and structure. These changes have been most marked since the 19th century explorers first saw the place.