The long-term persistence of old trees in human-dominated landscapes
nature.com
nature.com
I’m cities across India where there are limited protections for flora and fauna, one can often see trees seen favorably in religion or even unfavorable in religion, survive while others perish. Trees that are viewed unfavorably are especially interesting. Peepal or Ficus religiosa is believed to harbor evil spirits in the folklore. You’d expect it to disappear from the landscape, but counterintuitive to the idea, they are some of the most commonly found trees in the cities. Reason: no one wants to upset the evil spirits by cutting down the tree. It’s sometimes near impossible to find people willing to even trim the trees down to keep them safe.
> identified which species were most likely to persist as old trees in human-dominated landscapes and where they were most likely to occur. We found that species with greater potential height, smaller leaf size and diverse human utilization attributes had the highest probability of long-term persistence. The persistence probabilities of human-associated species (taxa with diverse human utilization attributes) were relatively high in intensively cultivated areas. Conversely, the persistence probabilities of spontaneous species (taxa with no human utilization attributes and which are not cultivated) were relatively high in mountainous areas or regions inhabited by ethnic minorities.
Unsurprising results, but it's interesting seeing it quantified.
(Submitted title was "Human activities drive long-term old trees in human-dominated landscapes".)
It seems rather important that the trees studied are in China and this is about natural history there. I was told casually that every natural forest in that part of the world has been substantially cut.. there is no "old growth" past some threshold.
Lastly, no mention of methods .. we are in an information age.
Amazonia itself has been called a "manufactured landscape". 10% of its soil is man-made terra preta. The distribution of many important plants like brazil nuts simply can't be explained without accounting for distributions of different peoples. 84% of all arboreal plants in the Amazon are known to be useful to humans[0] (edible, medicinal, etc). More likely than the Amazon magically just being a more special place is that the possibly 8-10 million[1] native inhabitants (pre colonial) selected and planted them.
California's increasingly dangerous wildfires are largely due to the fact that it banned traditional cultural burning (before California itself was even legally a state even!). These highly controlled "cool fires" got rid of fuel that now builds up and causes the devastating wildfires of today. They also cleaned rivers (due to the charcoal that was produced) and obviously helped acorns produce much larger bounties. These burns have been going on for at least 10k years so much of the flora is highly adapted. Some sage species can't even germinate without the presence of ashes. Despite this reliance on fire, they also simply can't handle the powerful wildfires of today
Many European colonists who came to Australia often described it as looking like a giant well-managed park. It turns out much of it really was. Similar to native Californians, complex fire regimes were often used for landscape management. But colonist writings also describe fields of pulled up grass that spanned out for many miles. It turned out aboriginals used hayricks to ripen seeds in the grass. They often grew native grains and would use it to make flour and bread.[2] If you'd like to read more, there's a great book on this topic called Black Emu: Dark Seed.
Everywhere you look humans have had to very tightly integrate into their ecosystems. This is why "conservation" practices are often criticized by indigenous activists for banning indigenous people from their lands. Our ecosystems are as dependent on us as we are on them and there's a desperate need for a more expansive definition of conservation that includes active interdependence with nature rather than trying to box away nature to preserve some idea of a "pristine landscape" that never actually existed
[0] https://journals.plos.org/plosone/article?id=10.1371/journal...
[1] https://sci-hub.se/https://www.jstor.org/stable/24395921
But is a convenient myth, as a justification to chop it.
Animals also spread seeds and nuts.
> Of course once we first arrived in South America, only about 20,000 years ago, we had quite profound impacts on the Amazon's species composition and distribution, but... that's a mere 20,000 years ago
Consider the fact that only just 12,000 years ago the Amazon transitioned from mostly grasslands to the full-fledged continent-wide jungle it is today. Or that the last African humid period ended just 6,000 years ago during which the Sahara was covered with wetlands, grasses, trees, etc.
A LOT can change in just a few thousand years
> Before that, there was certainly a highly biodiverse and to all intents modern Amazon pre-dating humans by millions of years
Sure, if we're talking on the scale of millions of years we can include a jungled Arctic which also ended 50 millions ago (around the same age as the Amazon). I did not intend to argue humans were necessary to biodiversity or even to the Amazon's development. Rather just that they clearly left a major impact. From that first paper I linked:
> We found that half of the arboreal species (2,253) are useful to humans, which represents 84% of the estimated individuals in Amazonian forests. Useful species have mean populations sizes six times larger than non-useful species, and their abundance is related with the probability of usefulness. Incipiently domesticated species are the most abundant
Of course naturally people will often use the most abundant species (the paper addresses that as well), but it's hard to deny that the millions of native Homo sapiens acted as a keystone species. The recent advances in Lidar technologies especially have revealed an Amazonian landscape and soil distribution that's been deeply shaped by human inhabitation.
> if we could go back, we could still find regions plainly characteristic of every major present-day Amazonian ecotype, minus humans
This seems like an incredibly hard claim to back up but I would be absolutely delighted to read through any papers or books on the topic if you have them on hand
> This applies even more so to the much more ancient central African and southeast Asian rainforests in which there are also some areas with no clear record of inhabitation
Yes, apologies if I seemed to imply that every corner of earth was shaped by humans. This is certainly not true. I did not mention the landscapes you brought up, but I stand by the claim that there is plenty of evidence that the 3 case studies I brought up are heavily shaped by human culture despite often being portrayed as "untouched" environments
> But to them we're a recent development.
I completely agree with this statement but go back to my first point (and I even made the point without bringing up climate change!)
Google says the Amazon rainforest is 10 million years old.
These are orders of magnitude different. Maybe they are using different definition or sub-regions.
>The arrival of European diseases after Columbus crossed the Atlantic in 1492 may also have hastened the growth of forests by killing indigenous people farming the region, the scientists wrote in the U.S. journal Proceedings of the National Academy of Sciences (PNAS).
It would be very lucky for humans to be so devastating[1] to the natural environment everywhere except the Amazon and yet have been excellent stewards of the natural environment within the Amazon. Such assumptions smack of the "noble savage" mythology.
1: https://en.wikipedia.org/wiki/Quaternary_extinction_event
Not sure how that's relevant to the sentence you quoted though. The Amazon rainforest has been largely savanna type ecosystems at various points in its history. Including quite recently (like 12kya)
Because the California fires of yore would roll through on a regular basis burning the limited fuel on the ground and not getting hot enough to damage the trees.
Now, after preventing natural burning for quite a while, there’s plenty of fuel sitting on the forest floor to get hot enough to kill all the trees.
No humans needed, lightning strikes are all you need to clear the forest floor every so often and keep the trees happy assuming you let nature take its course.
I don’t doubt that humans would clear land by burning but I do doubt that they had enough of an impact to change the entire ecosystem in the limited amount of time they were there.
Ecosystems and environments change. Quite rapidly sometimes
> the California fires of yore would roll through on a regular basis burning the limited fuel on the ground and not getting hot enough to damage the trees
Yes that's exactly the point of the cultural burns
Humans banned water based ecosystems, and substitute them for fire based ecosystems. The brilliant results had been always the same. Big desert in Sahara, Big desert in Australia and parts of Asia. Brazil has some human made deserts also.
Keep committing the same error by inertia, because is what they did in the middle age, and expecting different results is foolish. We need to pause and think twice why we want to send all this CO2 into the air.