[solardev]

I dunno why you were flagged. It's a totally valid question IMO, and I asked it a lot in school too (environmental science undergrad). To me, the difference is the RATE of change and expansion.

Nature and evolution can pretty easily deal with small changes in small areas happening over hundreds or thousands of years, which was normal before human population explosions.

But when that change happens across multiple human settlements (large areas), quickly (industrialization and the green revolution in just a few decades), and at a huge scale (not just cats but climate change and deforestation and pollution all leading to habitat loss), it is very very hard for other species to cope.

If a few individual wildcats crossed a land bridge, sure, they'll have a field day as they gorge on unsuspecting prey. They'll do well and reproduce, and their kittens will eat more prey. But eventually there are more wildcats than prey, a harsh winter or drought comes along, and a bunch of kittens die and the prey have a chance to recover over the next few years. It reaches a dynamic equilibrium.

That's different than when humans settle a new place and suddenly introduce hordes of rats and start breeding pet cats, at numbers far above what the prey population can sustain (because we feed them pet food). The unwanted ones become feral and enter the system at a rate higher than they would've through normal migration, and then we keep breeding more and more of them with an outside input (more pet food). Pretty quickly the feral cats will kill off a lot of the unsuspecting prey (the dumber, more exotic birds, often) and leave a bunch of human-adopted species like rats and corvids and squirrels that can coexist with cats, often having immigrated with the humans for hundreds of years. So you end up swapping the local wildlife for the introduced ones in just a decade or two, way faster than the dozens or hundreds of years it usually takes.

On islands or where settlements and road networks form unnatural barriers, this is especially bad because the escaping prey have nowhere to run to, being isolated to smaller non-contiguos pockets that can individually be trapped until the whole species is extinct or at least extricated (locally extinct).

Of course there are gray areas. The Hawaiian Islands, for example, are a mix of species that ended up there naturally, some a long time ago, some more recently. They have different times of introduction, just like humans do. But because it's a young island chain (in geologic time), its whole timeline is compressed and the species there have different, eh, degrees of "native"-ness, I guess. And among the various introduced species, not all of them are considered invasive. https://dlnr.hawaii.gov/hisc/info/

Anyway, it's not an exactly cutoff date or algorithmic formula for determining nativeness. It's just a case by case judgment call based on the relative time of introduction compared to the ecosystem age, and also the effects of the introduced species on other preexisting ones. It's a human judgment call subject to errors, like any others, but still a useful consideration in ecology.

Sorry for the long post...

[wtflick]

I agree with most all of that, and maybe a different way to frame it is, 'human induced changes in ecosystems can cause problems for humans'

I don't really agree its damaging to or causing problems for nature/ecosystems, or that its unnatural, because it implies that humans themselves are not part of nature or ecosystems, that we are something different in kind than the rest of nature (you can argue this in some dimensions sure). I don't think humans settling a new place and introducing bands of cats who are fed from petfood is _that_ different from a landbridge opening up for a couple of centuries. Things will stabilise it's just a matter of timeline.

I think maybe the part that annoys me is that it's humans trying to control the ecosystem under the guise of keeping it in some idealised 'natural state' when that's cleary not a thing in nature, and how we end up having people advocating mandatory neutering of cats and dogs and laws that people must keep cats inside, practises which kinda disturb me tbh.

[solardev]

> human induced changes in ecosystems can cause problems for humans

I mean, there's totally some degree of selfishness in us wanting to keep nature at some idealized level of "pristine": It has value to us as humans, both in terms of resources and ecosystem services, but also just at an emotional level -- some of us really value nature (as we roughly know it).

Even if you don't use loaded terms like "damaging" or "unnatural", you can still objectively measure a decrease in biodiversity (as in the # of different kinds and numbers of inter-species populations and cross-dependencies and an ecosystem's overall ability to respond dynamically to challenging events like harsh weather or wildfire). When big changes are introduced to a small system too quickly for it to handle, it doesn't so much matter what you call it... the same thing typically still happens: local flora and fauna, which are often endemic to an area (only found there), are displaced by "generic" versatile scavenger species like rats, pigeons, and crows. (Or in this case, predatory cats).

Is a marbled murrelet, a kind of bird, more worthy of preservation than the common crow? I guess that depends on who you ask. Yes, there's some amount of value judgment there -- most of us don't want to see a world with only like twenty remaining species because we killed the rest. We don't have de-extinction technology yet either, and we don't have the capability to regrow old-growth forests in human bureaucratic lifespans. It's true that we don't have all the answers, and all the proper "values" so to speak, to be able to measure the worth of any one species over another, necessarily.

> I don't really agree its damaging to or causing problems for nature/ecosystems, or that its unnatural

But even then, there are some we know to be "keystone" species whose disappearance will cause cascading effects across its local ecosystem, while others just have roles we don't fully understand yet (or maybe really are just "worthless"). But once we kill them off, we don't have any way to bring them back, and that's a few million years of evolution potentially lost forever. A simple precautionary principle might also apply there; we shouldn't necessarily go around destroying everything just because we don't see its immediate value or how other parts of the system depend on it.

This is the kind of thriving, diverse life that many people, environmentalists or not, value. Is it "natural"? If you don't like that word, don't use it, and maybe biodiversity is another metric we can use instead? Does THAT have value? Again, it's a judgment.

A roundish rock with magma lakes is also "natural", but it's not exactly teeming with life. A planet with only microbes is also alive, but not very diverse. Or a city with only imported palm trees and glass windows. The modern web of life took a looooooong time to get to this point, but we can easily lose a lot of it in a few short years. A lot of species value biodiversity -- not just humans, but many animals will prefer certain kinds of forests over others, and decomposers will converge on different kinds of debris, different birds have favorite foods, etc. -- life begets more life. If you don't value any of that, that's totally within your rights, but maybe I'd ask "Why not?"

Is it that you really love cats, and don't want to keep them inside all the time? (I have a cat too and I feel bad that it's an indoor cat... but for entirely different reasons, not biodiversity). Even then there are tools to limit the damage they can cause (like silly poofy collars that birds can easily see: https://www.birdsbesafe.com/)

Do you just not care for nature, feeling kinda meh about trees and birds and shit? That's fine, though it does seem like jumping to conclusions a bit quickly. How do we know these things are worthless?

Is it a more philosophical stance on nihilism and accelerationism...? Like if "nature" goes through cycles and things live and die and eventually our sun will burn out and entropy will increase and the universe will reach its heat death anyway, what does it matter what we do now?

I dunno. I shouldn't put words into your mouth. What do you think?