AMA with Stanford biologist Paul Ehrlich: How the Border Wall Threatens National Security
Aug 9, 2018

A Border Wall Threatens Our National Security

The continuous border wall President Trump has pledged to build could cause the extinction of various plant and animal species, damaging natural services to people and local economies in the process. It would be a crime against biodiversity.

I am co-author of a recently published analysis that outlines how physical barriers prevent or discourage animals from accessing food, water, mates and other critical resources by disrupting annual or seasonal migration and dispersal routes. 

Nearly 3,000 scientists have signed on to endorse the paper’s message, which includes a call for solutions such as requirements that the U.S. Department of Homeland Security identify species, habitats and ecological resources at risk from barrier construction and security operations; design barriers for maximum wildlife permeability where possible; and purchase or restore replacement habitat when environmental harm is inevitable.  ( will be posting my responses to questions)

Read more about the study.

Read about The Millennium Alliance for Humanity and the Biosphere, which I lead.

Read about the Stanford Center for Conservation Biology, which I lead.

My bio.


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Is it really possible to stop the construction of the border wall? What are the reasons behind your answer?
Aug 11, 11:28AM EDT0
What are the regions that are going to be the most vulnerable?
Aug 11, 9:17AM EDT0
What are some of the international honours you have received for your work in the past and how has your popularity or prestige in the science community made it easier for you to get other scientists involved in your analysis?
Aug 11, 3:29AM EDT0
How does one become a member of the National Academy of Sciences and in what ways has this membership aided you in your current research?
Aug 11, 3:12AM EDT0
Can you share an example of any country where the border wall created serious wildlife concerns?
Aug 11, 2:47AM EDT0
If the wall was finished today, how much time would be there before the impact on biodiversity is irreversible?
Aug 10, 7:44PM EDT0
Which species would have their migratory route cut off with the construction of this border wall?
Aug 9, 5:24PM EDT0
Nearly 3,000 scientists have signed on to endorse the paper’s message. How will it benefit you with work?
Aug 9, 3:21PM EDT0

It may benefit my grandchildren by helping encourage citizens to get rid of the Trump administration that is working so hard and and so effectively to destroy civilization. 

Aug 9, 3:30PM EDT0

Is there any evidence so far of animals moving north due to climate change?

Aug 9, 1:44PM EDT0

There is abundnat evidence, much reported in the peer-reviewed scientific literature, that animal populations in the northern hemisphere are tending to move north and also to move higher in mountain ranges.

Aug 9, 1:50PM EDT0
How many different species of insects are estimated to inhabit the ecoregions spanning the US-Mexico border? How would the border wall affect them?
Aug 9, 8:33AM EDT0

No one knows the number, but it's certainly many. A wall would affect many of them by reducing habitat and population numbers and therefore increasing chances of extinction. By extension, it would reduce the bird supply of many birds that depend on insects for food.

Aug 9, 1:16PM EDT0
If the border wall was built, could the most affected populations be restored through a comprehensive (and equally massive) government-funded conservation initiative that includes breeding and wildlife reintroduction? What are the reasons behind your answer?
Aug 9, 1:50AM EDT0

I kow of no such massive government effort in North America to preserve biodiversity. The best attempt to keep track of biodiversity on the continent is by the government of Mexico. There's no reason to believe the current U.S. administration would do anything to remediate the impacts of a wall. Destruction of biodiversity is very difficult and expensive to correct in almost all circumstances.

Aug 9, 1:14PM EDT0
How larger the populations of jaguar and ocelot need to be in the US-side of the border to ensure the establishment of independent populations after the placement of the wall?
Aug 8, 6:17PM EDT0

Much larger than we think they are now. It's not even clear there's enough usable habitat on either side. I would refer you to Gerardo Ceballos, a renowned biologist at UNAM:

Aug 9, 1:11PM EDT0
Which bodies of water would be blocked from one side or the other of the wall?
Aug 8, 12:16PM EDT0

You can see a map of the border here:

Beyond permanent bodies of water, many temporary flows may be interrupted.

Aug 9, 1:09PM EDT0
Since most angiosperms use aerial pollination vectors, which plant species would be directly affected by the restricted transit of terrestrial pollinators?
Aug 8, 6:27AM EDT0

That's a question for a botanist.

Aug 9, 1:05PM EDT0

Has the current border wall have some effect on the wildlife so far?

Aug 7, 7:28PM EDT0

By definition, yes. If you build a wall, you are going to have an effect on wildlife.

Aug 9, 1:05PM EDT0
What options are there that ensure wildlife permeability through the wall?
Aug 7, 9:20AM EDT0

Basically, none, because wildlife is a multiplicity of things. What would make the wall permeable to a medium size mammal would make it permeable to human beings.

Aug 9, 1:03PM EDT0
While border walls are dangerous for the current biodiversity, it is possible to see them as a driving force for speciation through allopatric and parapatric mechanisms. What are the ethical concerns related to this idea?
Aug 6, 5:28PM EDT0

Speciation mostly takes hundreds to millions of years, extinction is in the next two decades.  Looking to the wall as a driver of speciation to perhaps balance the extinctions is nonsense.  The ethical concerns circle around what economists call “moral hazard,”  making people feel more comfortable with the destructive acts.

Aug 6, 6:05PM EDT0
What kind of ecoregions would be affected by the construction of the border wall?
Aug 6, 5:19PM EDT0

There is a wide range, from temperate to tropical, marine, freshwater, wetlands, etc.

Aug 9, 12:57PM EDT0
What plant species would be directly affected by the wall?
Aug 6, 4:21AM EDT0

All species growing near the wall – there are very many.

Aug 6, 5:17PM EDT0
What would be the most effective solution to ensure a positive conservation strategy in this region?
Aug 3, 11:55AM EDT0

Vote against every and all Republicans in the November 2018 elections.  The party under Trump is dedicated to destroying humanity’s life-support systems, and is much worse than the Democrats in dealing with the complex and ethically charged human issues related to migrating people.

Aug 6, 5:18PM EDT0
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