Biodiversity conservation in a human world: do successes involve losses?

It's become commonplace to state that the world is in the midst of a mass extinction event. And there is no doubt about the cause. Unlike previous mass extinction events, like the cretaceous extinction event that saw most dinosaurs disappear, the current extinction event is not caused by a geological or astrological event. Rather, the current extinction event is caused by a single species, humans. Through habitat destruction, wildlife harvesting, pollution, and the introduction of pest species to other regions, the current extinction rate is 100 to 1000 times higher than it should normally be. We often think of human legacy in terms of art or architecture, but a permanent scar in the biological record of the Earth is our greatest legacy.

Of course many people and some governments are very concerned about our impact, and have committed to try to conserve elements of the remaining natural world. How best to do this is largely influenced by conservation biology, a field of research and applied management that includes biology, economics, and sociology, amongst others. There are many debates within conservation biology, and a big one is about how much to involve people, and their activities, in conservation areas versus attempting to completely exclude people from protected areas.

Two conservation conversations have explored this dichotomy in meaningful ways. First is a recent paper by Elena Bennett (Bennett 2017), who argues that strategies for environment and conservation protection needs to take a human-first approach and focus on human well-being. The second is a talk I saw from Daniel Janzen the other day. Janzen is a world-renowned ecologist and has dedicated his life to conservation in Costa Rica for the past 30 years. This debate was central to his talk about the conservation successes at the Area de Conservacion Guanacaste (ACG), where Janzen developed and implemented a conservation philosophy that included local people in the managing and research in the conservation area. Before Janzen, the Park relied on the traditional approach of excluding people to protect nature and it was failing. Janzen’s approach has been immensely successful, and the Park is now considered a conservation success story.

People can be convinced to appreciate biodiversity around
-if it provides a benefit. (photo by M. Cadotte)

Including people in nature conservation is bound to have successes. People feel more familiar and involved with nature protection, which gives them a sense of ownership. If people understand the benefits of nature, economic and otherwise, then they will be invested in its protection. It all seems so logical, but as I listened to Janzen’s talk (and read Bennett’s paper), I kept thinking: “would there be any losers under a human-first approach to conservation”. I think the answer is yes, and the reason is that we are prone to use a shifting baseline to evaluate success. Let me explain what I mean.

The human-nature story is one that is about a continual 30,000 year retreat. All of our successes -our population growth, our art, our medicine, have all come at the expense of nature. Anywhere on Earth where there are humans, there are losses. Habitat alteration and destruction, and species extinctions are the defining feature of our presence. This legacy has permanently altered the biology of our planet.

Why is this important? Because we really don’t care. We don’t miss wholly mammoths in northern Europe. We don’t miss giant sloths in California. We don’t miss black bears in downtown Toronto. We don’t miss lions in Cape Town. The definition and acceptance of nature  for most people is not influenced by what is not there, but rather the critters we are familiar with and are willing to accept. Big mammals simply have no place in human dominated landscapes and we don’t bemoan their absences.

Can human-first conservation protect jaguars?
(Photo from wikipedia)

Human-first conservation strategies work simply because we accept a less valuable system as acceptable and perhaps normal because of our shifting baselines. Would a human-first conservation strategy work in Costa Rica’s ACG if there was a huge jaguar population that was attacking livestock? Not likely.

The United States government spends billions on national parks to conserve nature (among other things), but if it was up to ranchers living near Yellowstone, for example, all the top predators will be exterminated. Hunters and ranchers in Germany are similarly up in arms (literally) over the re-appearance of wolves and lynx in restored forests within Germany’s borders. Some there consider the extermination of large predators a commendable feat of an advanced society.

The point is that we like the nature we know, and the nature that is not likely to kill us. People are most often invested, familiar, and willing to conserve nature around them, which already works for them.

Costa Rica’s ACG human-first conservation works in certain contexts. It gets people involved, it protects certain facets of nature, and it has a high likelihood of long-term success. If this is the model for a successful conservation philosophy, then we must accept that not all of nature can be protected. In all likelihood, many large mammals will go extinct in my childrens’ lifetime, regardless of how well we do conservation. So perhaps, moving forward with the human-first strategy is the best option, but a part of me hopes that there is a place for real nature in our world. The rest of me knows that there isn’t.


Bennett, E. M. 2017. Changing the agriculture and environment conversation. Nature Ecology & Evolution 1:0018.

Valuing Toronto's urban forest: seeing the forest for the trees

Many news outlets in Toronto reported on a study released by the chief economist at TD bank about the value of urban trees in Toronto. Toronto has been called ‘the city in a park’ because of the heavily forested urban landscape we have here (though when you Google ‘city in a park’ a plethora of cities have the same view of themselves). The value of Toronto’s urban forest estimated by the economists was 7 billion dollars. This seems like an astronomical amount, and that a large bank is the one forwarding this view of the value of an urban forest is in itself an amazing development (note: I do have an obvious conflict of interest as my professorship is endowed by TD).

TD's valuation of the urban forest relied on per-species estimates of net benefits, including carbon sequestration, air quality improvement, storm water flow, and energy savings though shading of buildings. These economic returns more than justify municipal expenses for maintaining parks and urban trees. This approach to quantifying the value of trees has been forwarded by new initiatives such as iTree that provide information on the benefits of tree species. The TD report does go on to say that there are other unquantified benefits of the urban forest such as aesthetic values and importance to communities. But the question is, is cumulative economic benefit a sum of individual trees or is there something more to a forest?

While individual trees have clear economic benefits, captured nicely in the report, and which often increase with the age or size of the tree, there may be direct economic benefit from forested lands that is greater than the sum of the individual trees. In essence, we need to see the additional value of the forest for the trees. Individual trees do not make a forest, and there is something special about a forest.

The simplest way in which a forest supplies additional value is through diversity effects. Different tree species may utilize differing resources or niches and by occurring together are able to turn more of the total local resources into growth, thus sequestering more carbon dioxide then if they were grown alone or only with other trees of the same species. As an example, if you grow a tall canopy tree and a medium shade tolerant species underneath it, the cumulative energy savings through shading are much greater than growing two tall canopy trees or two medium shade tolerant trees. This is often referred to as ‘complementarity’

Photo I took while on a hike in Toronto's Rouge National Urban Park

More than species complementing one another, in forests we often see species facilitating one another, meaning that individual trees perform better with other tree species around it, then when grown alone. Again, using carbon sequestration as the example, facilitation means that more carbon is taken up then when trees are isolated from one another.

Forests also provide habit for other plants and animals that individual trees do not provide. A forest can also better support pollinators by including different tree species that flower at different times of the season. Further, forests provide recreational activities (biking, hiking, camping, etc.) that are economically measurable (gas costs to travel there, user fees, tax support, etc.).

Taken all together, intact forests supply even greater economic, health, and environmental benefits than individual trees. If the trees of Toronto are valued at 7 billion dollars, then the forests of Toronto must be worth much more.