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Comment by jacquesm | Hacker News Reader

This is not exactly a new finding, and one of the reasons the ecoduct was invented.

https://en.wikipedia.org/wiki/Wildlife_crossing

They work just as well for forests as for other biotopes but the countries where the forests end up slashed into pieces tend not to have the funds to reconnect them.

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The article does clear up why different studies found the effects of fragmentation differs:

> While many studies have shown that extinctions are more common in fragmented environments, others haven’t documented much effect.

> A study published on Thursday may help resolve what has been a strident debate, showing why many species are vulnerable to the fragmenting of forests while others are not. Animals in places with a long history of disturbances are relatively resilient, the researchers found. Species that have existed in stable habitats for thousands of years are far more sensitive.

This may affect where you decide to put wildlife crossing or justify building such crossing.

Countries may want to build those but may not be able to afford them.

And, as the article writes, the forests in regions with a long history of undisturbed forests (Java, Brazil) contain species that will not leave the twilight of the forest canopy, so I doubt a wildlife crossing would benefit them. Apparently even birds that could easily fly from one "segment" to the next will not do it because they shy away from the open areas.

I like the idea of wilderness corridors: narrow connective parks linking larger undeveloped areas.

It's a good idea with one major problem, predators soon figure out that other wildlife has to pass this choke point and they will treat it like a walking buffet.

Not sure that's a major problem? Predators are generally the animals with the larger territorial requirements for a home range, and thus more reliant on the presence of these corridors to feed and disperse into new territory.

It negates the usefulness of the concept.

The concept is still useful but without the travel corridors when it comes to birds. Here it is encouraged to put even small blocks of land into a permanent wildlife covenant. Birds can use them as oases.

To some extent, plenty of bird species do not like to overfly humanity at low altitude and if the area isn't large enough to gain altitude or if the motivation isn't strong enough to expend that much energy then there might was well be a cloud high fence.

True, perhaps this approach would not work for condors, eagles etc.

However for most native birds in my country even a spot of an acre or two can be a good bird habitat for nesting and feeding and birds will happily overfly humanity to get to and fro.

The risk is it solves just one of the multiple issues from fragmentation and rather than preserve you develop something entirely and completely different. We will have to see in a century or three whether what results is desirable.

The smaller species of plants and animals in the forest food chain migrate slowly - perhaps a few inches or feet a year, and forest edges are different. Not least they have vastly more light than within the depths of the forest. The carbon uptake is less - thanks to that increased light, the decomposition cycle is different, and less of the dead wood gets broken up to go deep into the soil. By creating lots of little islands with only edge forest, you no longer have the true forest - that far enough into the canopy that deep forest rules apply - the forest that in theory we wanted to save. A connecting strip between areas risks multiplying that edge forest effect dramatically - trapping deep forest species just as surely as an eight lane road or city in the way.

Without a contiguous forest in which to exist, those isolated islands start to evolve differently. In the case of tropical and temperate rainforest you need the huge expanse or you lose the climate impacting effects. e.g. one tree takes up some number of litres of water in the growing season, and you need n trees to seed enough clouds to remain rain forest, or put enough terpines in the air (particularly coniferous) to preserve the right balance of insects.

It's these climate impacting effects - the water uptake and cloud seeding, that is one of the main reasons many studies are claiming the Amazon is nearing a tipping point into catastrophic drying.

TL;DR we really need to develop the will to preserve and remake unfragmented, untouched - or at least limited - wilderness forest - for the benefit of all of us.

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