Thread by @ZoologyDave

There's a lot of #badnews about #biodiversity and #conservation at the moment, so how about some #conservationoptimism? 🧵 based on our new paper pnas.org/doi/full/10.10… and some awesome recent work by others... 1/

As you probably know, the world has ambitious targets to protect 17% of the world's land for #biodiversity #conservation, and there are calls to increase this to anywhere between 26-60% in the next round of @UNBiodiversity talks (this year) 2/

In theory, this is great for biodiversity (more on the human impacts later). Problem is that the total area of land that you protect may not be important: a lot of #protectedareas are small or isolated, and this means that the populations are also small and isolated 3/

(this is what this awesome paper led by @brennan_angie, @clairekremen and others showed last week: science.org/doi/10.1126/sc…) 4/

Small isolated populations aren't going to last a long time (they aren't "viable"), and so don't really count towards providing long-term protection from #extinction. Instead, they will just cling on for a while and eventually die out 5/

So we asked "how many of the world's #mammals are likely to survive in the #protectedareas that we already have?" ~15% of the world's land is in PAs, and a lot are focused on mammals. If #conservation is going to work for anything, it'll be mammals 6/

To do this, we simply overlaid maps of suitable habitat for ~4000 species of mammal (thanks @carlo_rondinini!) on top of PA locations from @protectedplanet/@IUCN_PA) and used @L_Santini_Eco's wizardry to estimate the density and population of each species in each PA ... 7/

...and then estimated whether each population could survive in the long-term or not. 8/

What we found was that around half of all mammals simply don't have large enough chunks of habitat protected to survive in the long-run, despite us getting pretty close to that 17% target 9/

Almost all the world's #threatened mammals (i.e. those we should be most worried about) had ≤10 viable protected populations across the world, but so did ~1000 species not currently threatened. 10/

This is seriously #badnews for biodiversity and chimes with @jamesecology's recent paper (with @stubutchart @HugePossum @GwiliGibbon et al) which found that meeting biodiversity targets could take 44% of all the world's land science.org/doi/10.1126/sc… 11/

Our analysis emphasizes the need to think about the size of individual habitat patches (the ecological spatial structure of populations). Focusing on total area protected, even scaled for individual species (the current go-to approach) doesn't capture habitat #fragmentation 12/

And we demonstrate that this #fragmentation is at least as big a threat to long-term survival as #habitatloss 13/

OK, so what do we do? Well "protected more land" seems obvious, but this has HUGE costs: both directly to the people who live in or manage these areas, and indirectly in terms of restricting what people can do (the opportunity costs) 14/

Other people have written far better about this (e.g. @csandbrook, @PaulRobbins15, @danbrockington, @_GeorgeHolmes), so I won't mangle their words, but this is a massive issue 15/

But, I'll add that these costs are about to get a LOT bigger and harder to avoid. Last year we projected agricultural expansion across the world and its #biodiversity impacts and it does not look good at all (nature.com/articles/s4189…) 16/

So where is the #conservationoptimism? Well... I lied. It's really quite bad news. But I do think there are glimmers of hope... 17/

If we really push for a few key interventions (dietary shifts in Europe and N America, yield increases in Africa, reducing food loss everywhere) then we reckon we can #feedtheworld without widespread habitat loss (nature.com/articles/s4189…) 18/

And if we do this, and are careful about planning where agriculture, urbanisation, mining etc. develop, and make clever, strategic decisions about which land we protect, and how we protect it, then we should be able to provide for everyone whilst conserving #biodiversity 19/

But we need to think about those individual species populations. Think about the ecological reality and the spatial structure of what we're protecting, or we'll just end up with tiny fragmented populations, doomed to extinction 20/

And of course, any new protection or management HAS to be an inclusive process, bringing in #indigenous communities, local people, and those who use the land, to ensure that it is fair, equitable, and supports people as well as #biodiversity.

Right, that's quite enough! 21/21