We are liv­ing in the cen­tu­ry of urban­iza­tion. By 2050, 70% of the world’s nine bil­lion peo­ple will be liv­ing in cities. 

Cities form a vast glob­al net­work con­nect­ed by flows of ener­gy, food, infor­ma­tion. This glob­al net­work is the chal­lenge of the 21^st cen­tu­ry. How do we make more sus­tain­able cities, with small­er eco­log­i­cal foot­prints and more equi­table human wellbeing?

Today I want to stress the link­ages between cities and ecosys­tems. Cities rely upon the goods and ser­vices pro­duced by bio­log­i­cal diver­si­ty embed­ded in ecosys­tems. These ben­e­fits are called ecosys­tem ser­vices. But, as cities draw upon these resources not only do they clear the land and trans­form the land­scape, but they also frag­ment and dis­con­nect ecosystems.

This loss of eco­log­i­cal con­nec­tiv­i­ty erodes bio­log­i­cal diver­si­ty and degrades the very ecosys­tem ser­vices we need for sus­tain­able cities. This hap­pens at a glob­al scale; there are glob­al tele­con­nec­tions between cities and landscapes.

But it also hap­pens at the scale of a city. So, here I am show­ing you analy­sis we did of how we eco­log­i­cal con­nec­tiv­i­ty (shown in red here) has been erod­ed over fifty years for the city of Montreal. So you can see this red patent is dis­si­pat­ing. Patterns of growth like this are com­mon the world over, and they are dimin­ish­ing the con­tri­bu­tion of ecosys­tems to city sustainability.

What we have here is a non­lin­ear rela­tion­ship between urban growth and urban con­nec­tiv­i­ty, and eco­log­i­cal con­nec­tiv­i­ty on the oth­er hand. It describes a tip­ping point, a non­lin­ear­i­ty in which beyond a cer­tain thresh­old of urban con­nec­tiv­i­ty, we lose the ecosys­tem’s con­nect­ed prop­er­ties. We need sci­ence that can slow and even reverse tip­ping points like this.

My research group at McGill University has used the­o­ry and exper­i­ments in the lab and the field to demon­strate how dis­con­nect­ing ecosys­tem net­works erodes diver­si­ty, lim­its pro­duc­tiv­i­ty, and affects their adaptability. 

But we can use net­work size to recon­nect them. And if we recon­nect them, we can restore many of these prop­er­ties in time. At the scale of entire cities, we’re col­lect­ing data to show how ecosys­tems embed­ded in cities like Singapore affects air qual­i­ty, urban heat extremes, and bio­log­i­cal diver­si­ty and how it medi­ates process­es like pol­li­na­tion, pest con­trol, and the microbes that affect the well­be­ing of our very immune systems.

Back in 2009, I received a remark­able request from the Quebec gov­ern­ment. They asked if I would apply my research to the design of an eco­log­i­cal net­work for Montreal and the region—the 27,000 square kilo­me­ter region—around it. You can imag­ine that was a lit­tle bit daunt­ed by the scale of this request. I hes­i­tat­ed. But after some hes­i­ta­tion, I real­ized that I have to do it. I think net­work sci­ence is both pro­found and practical.

So how did we do that? We com­bined bio­di­ver­si­ty sci­ence and net­work sci­ence, and many dif­fer­ent land cov­er data on habi­tat qual­i­ty, ecosys­tem qual­i­ty, and the needs of many species. And then we com­bined pro­jec­tions from region­al cli­mate mod­els and our own land use change mod­els to assess how con­nec­tiv­i­ty has changed in the past, how it is today, and how it will be in the future.

Our method­ol­o­gy allows us not only to iden­ti­fy con­nec­tiv­i­ty, but also esti­mate the con­tri­bu­tion of each ecosys­tem to the con­nec­tiv­i­ty of the whole sys­tem. So we have like a weight­ing. Which frag­ments are more impor­tant or less impor­tant to the con­nec­tiv­i­ty and the con­tri­bu­tion of ser­vices to the whole.

So, here I’m show­ing you one such map. The res­o­lu­tion is 30×30 meters, and I’m show­ing you the con­tri­bu­tion of every pix­el to the con­nec­tiv­i­ty of the region’s net­work. And in dark green you see the ecosys­tems of high val­ue, high con­nec­tiv­i­ty. And zones in red of low connectivity. 

But what will the region look like in 2050? Here I’m show­ing you a sce­nario, a busi­ness as usu­al sce­nario, in which land use change and cli­mate change have con­tin­ued unchecked. Now you see many few­er dark green frag­ments, and the region’s eco­log­i­cal con­nec­tiv­i­ty has passed the point of sustainability.

We can also use our method­ol­o­gy to iden­ti­fy ecosys­tems that con­tribute mul­ti­ple ben­e­fits. So in this instance, on the left there I’m show­ing you ecosys­tems in light green that not only main­tain bio­di­ver­si­ty but they also mit­i­gate urban heat extremes, which cause fatal­i­ty in the sum­mer months.

This approach has allowed us to start a new dis­cus­sion with gov­ern­ment, with the city, and NGOs and busi­ness­es. Because we can show them that by pro­tect­ing just 17% of this net­work, we can main­tain 75% of the region’s con­nec­tiv­i­ty. So we’re work­ing with these part­ners and stake­hold­ers to re-vision the city’s green­belt as an eco­log­i­cal network.

Science like this I think should be applied to any city. That’s my vision. I think we should be export­ing this method to any city in any part of the world. Connectivity sci­ence and man­ag­ing con­nec­tiv­i­ty as cities grow will be an essen­tial part of the solu­tions for urban sus­tain­abil­i­ty in the 21^st cen­tu­ry. Managing eco­log­i­cal con­nec­tiv­i­ty is one set of the solu­tions that I think is essen­tial for sus­tain­abil­i­ty, and sus­tain­abil­i­ty ulti­mate­ly is fun­da­men­tal to our col­lec­tive, con­nect­ed futures. Thank you very much.