Biodiversity

The American Museum of Natural History in New York defines biodiversity thus:

The term biodiversity (from 'biological diversity') refers to the variety of life on Earth at all its levels, from genes to ecosystems, and can encompass the evolutionary, ecological, and cultural processes that sustain life. Biodiversity includes not only species we consider rare, threatened, or endangered, but also every living thing — from humans to organisms we know little about, such as microbes, fungi, and invertebrates.
Source: U.S. Museum of Natural History

Biodiversity is the variety of life on earth, encompassing everything from the largest ecosystem to strands of DNA. It is in every living thing around us, and everything around us is part of it. I know, this all seems very poetic, and nature can be appreciated merely by virtue of its own beauty and diversity. But there are some practical, and even selfish reasons to care about biodiversity, as you will see in the readings below.

As you can see, there are many reasons to care about biodiversity. Aside from the huge economic benefits of ecosystem services, we depend on the biosphere - and by extension, biodiversity - to sustain human life. We depend on ecosystem services for food, shelter, clothing, water, and even our oxygen. So yeah, basically everything we need to physically survive!

Life on earth is connected in innumerable ways (systems thinking, y'all!), and compromising one part of an ecosystem - including a single organism - has impacts in other areas. Unfortunately, human activity is playing a major role in ecosystem damage, including species extinction. Wilson points out that:

"Species are disappearing at an accelerating rate through human action, primarily habitat destruction but also pollution and the introduction of exotic species into residual natural environments."

Humans are the main cause of the observed increase in extinction rates. Often, the impacts of this biodiversity loss are hard to predict. Donella Meadows, a well-regarded ecologist, pointed out a few of these in her essay "What is Biodiversity and Why Should We Care?".

• Reforestation of the African Sahel was found to be impossible because the degraded soil was deprived of a bacteria that Acacia trees require to grow.
• North American songbirds are in decline because the areas they live in over the winter in Central America are in decline.
• European forests are more vulnerable to disruption than American forests because they are less biodiverse.

Biodiversity is a key aspect of ecosystem services, and ecosystem services are essential for human survival. (If you need a review of ecosystem services, refer to the first part of this lesson.) One thing that makes biodiversity difficult to manage is that we don't know how many species exist, and by extension do not know exactly how many are going extinct each year.

Many would also argue that nature has value in and of itself, irrespective of how it helps humans. This is often referred to as ecocentrism or deep ecology, which we will not discuss in more detail (but is worth looking into if you are so inclined). Humans also enjoy nature in many noneconomic ways. The "beauty of nature" is a common phrase, and being in and around nature can be both enjoyable and therapeutic. Indeed, nature is known to be therapeutic, as people in the emerging field of eco-psychology are documenting. I imagine most of you have enjoyed the soothing calm of a forest, desert, ocean, or even backyard. It is difficult to put a monetary value on this, but it is valuable all the same. Biodiversity makes all of this possible, and destroying biodiversity puts all of it at risk.

The 6th Mass Extinction

So how much danger are we in, and how do we know? As it turns out, it is possible to measure - or at least scientifically estimate - the rate at which biodiversity is dropping. As Carl Foulke pointed out in Chapter 2 of Is Sustainability Still Possible?, the rate of biodiversity loss as one of "The Nine Planetary Boundaries." The metric used to quantify this loss is the background extinction rate, which is defined as the number of species going extinct every year. So, how are we doing on this front? Some recently published studies can shed some light on this issue.

It's not every day that you read a serious article that quotes a knowledgeable person as stating that: "What is at stake is really the state of humanity." Alas, that is where we find ourselves on this issue. There is unequivocal evidence that populations of many species have dropped considerably since humans became the dominant species, and as the article states, the background extinction rate is probably at least "100 times what would be considered normal" (see the optional reading above for some insight on this), which may be a conservative estimate. As indicated in the article, there is some controversy regarding this issue - the Atlantic article that Sutter links to provides a good, even-keeled assessment of some of them - but this primarily has to do with difficulty in determining the rate of extinction, and whether or not it should be considered a "mass extinction" or just a dangerous level of it. Any way you slice it, humans are causing species to go extinct at an accelerated rate for a variety of reasons, including land use change (especially food production), poaching, climate change, ocean acidification, and more.

It is important to point out that it is very unlikely that we have crossed an extinction threshold from which we cannot recover, but many signs point to us risking catastrophe. There is hope, but we will likely have to take action very quickly to prevent the worst outcome(s). Before this happens, it will have to be recognized as a problem, which unfortunately is only happening very slowly.