Pulitzer Prize winner, Elizabeth Kolbert, takes readers on a journey through Earth’s mass extinctions and the various anthropogenic forces that have lead scientists around the world to conclude that we are in the current ongoing 6th mass extinction. Kolbert reviews various ecosystems and species that are at risk, while reviewing past extinctions, comparing to current trends in climate change to the past to inform readers of the catastrophic impacts such trends have on biodiversity. Over 80% of current species are currently at risk of extinction as a result of some sort of human activity, indirect or direct. By analyzing humanity’s early history and its current impacts on the planet it is clear that human activity is speeding up species’ extinction rates.
Tracing early human history indicates that humanity has always had a substantial impact on the planet. DNA analysis shows that all humans except those from Africa have between 1-4% shared DNA with Neanderthals (“The Madness Gene”). This comes as a result of interspecies sex that we had with them creating hybrids that lived on to reproduce and eventually outperform Neanderthals, essentially killing them off. Small changes in our DNA sets us apart from earlier human species and chimpanzees (“The Madness Gene”). Kolbert plays around with the contention that the key change that allowed for modern humans to push past barriers and create their own carrying is ‘the madness gene’. Other differentiations such as culture have been made in order to understand why modern humans accelerated to become masters of the planet. (Heneghan).
Kolbert makes a point to use extinct species as a case study from which to draw conclusions about past extinctions and past life strategies. At the end of the Ordovician era, 84% of marine’s life died out (“Welcome to the Anthropocene”). Graphites was such a marine species that thrived during the Ordovician, it was specialized with a specific life history strategy that worked until climate changed (“Welcome to the Anthropocene”). The survivors of mass extinctions determine future species. Kolbert uses the megafauna case study to draw parallels to current big species such as rhinoceroses. Megafauna was depleted by small killings that eventually over thousands of years drove them to extinction (“Welcome to the Anthropocene”). Native people did not know the extent of the impact that these small killing would have in the future.
On another hand, current large land mammals follow similar life strategies. Suci the Sumatran Rhinoceros from the Cincinnati Zoo is one of the only Sumatran Rhinoceroses left in the world (“The Rhinoceros gets an Ultrasound”). Sumatran rhinoceroses have complicated mating rituals in addition to their life strategy of long gestation periods. Thus, it is extremely difficult for small populations to recover in captivity. Zoos have poor practices of transporting animals and of allowing diseases to reach at risk animalsimpact the limited populations of at risk species (“The Rhinoceros gets an Ultrasound”). The specialization of behavioral and physical traits will not work in an environment transformed by human activity resulting in grim outcomes for large species.
On another note, some species have mechanisms to ensure survival under changing environments, but these mechanisms are limited due to impacts of human land transformation. Kolbert surveys a case study in Peru’s Manu National Park, using Miles Silman’s 17 sites of forest as an example of our limited knowledge of species survival mechanisms. Silman’s 17 sites cover a range of climate for over a thousand trees species (“The Forest and its Trees”). In the past scientists such as Darwin believed that in response to stressors in a species’ habitat, continental scale migrations took place (“The Forest and its Trees”). Research conducted by Silman’s teams found that, similarly, species of trees will either move up sites or stay in place in response to rising global temperatures (“The Forest and its Trees”). The ones that stay in place are less likely to survive the impacts of human induced climate change.
This is significant as it shows that species will try to adapt their range to survive. In addition, there is a relationship between the area of habitat available and the amount of species found, regardless of our limited knowledge to how many species there are. The relationship is found to be non-linear (“The Forest and its Trees”). This impacts the availability of space for species the further up the mountain one goes. This is also important to consider when thinking about the impact this has on habitat fragmentation caused by humanity’s extreme land transformation (Heneghan). There is less diversity in smaller areas and they are less resilient under the threat of disease and outside factors affecting the ecosystem. Such limitations illustrate that while human activity causes climate change, other activities also limit species abilities to recover.
Human impacts on the environment are interconnected and its impact can be seen across ecosystems. Kolbert takes readers through a case study on One Tree island in the Great Barrier Reef. By nature, coral reefs are seen as “Darwin’s Paradox” (“Dropping Acid”). They are complicated structures that create their own home, thus sustaining vast biodiversity in an endless and often void ocean. These ecosystems are one of the most diverse systems on earth, hosting a home for these species but also needing the species to be able to stay resilient, thus are paradoxical (“Dropping Acid”). Like the Graphite’s and the megafauna, they too hold specific life strategies that have allowed for them to survive so long.
The polyps making up the reef are very sensitive to light, nutrients and acidity or aragonite saturation in the waters that they inhabit. Using a model of the Earth known as Biosphere 2, scientists were able to figure coral’s sensitivity to aragonite saturations (“Dropping Acid”). Coral reefs depend on saturations of aragonite between 4-5, yet current projections place no region above 3.5 by 2060 (“Dropping Acid”). Furthermore, they are also suffering bleaching and thus dying off due to rising global temperatures caused by climate change. They are ill equipped to maintain their resiliency due to overfishing and pollution caused by runoff and deforestation also lead to the killing off of species that help keep the reef’s resilience. Overfishing, pollution, climate change, are all interconnected in the way they impact the reefs and by the fact that they are all caused by human activity.
There is no argument to whether or not there is a loss to biodiversity. Despite this claim, substantial action may not be taken. If this was to be the case, then an extreme loss biodiversity will be seen in the coming few decades. The loss will be at a higher spectrum of predicted loss rates (Kolbert). The consequence of no action will furthermore result in our demise as a species (Kolbert). As a species that evolved using our own creativity, culture, madness, but perhaps above all, our ability to use other species and the earth’s own biochemistry to create our own carrying capacity, our own chances of survival in the 6th mass extinction are dire.
Thus, moving forward, legislation needs to be taken into consideration to stop habitat fragmentation, and unsustainable land transformation. A change of culture among businesses and manufacturers needs to occur in order to curb pollution and increasing carbon levels in the atmosphere. Without such laws to mitigate climate change and protect biodiversity, our species among with countless others are at extincion risk. Kolbert drives the point reminding readers that “it is unclear whether man and nature ever lived in harmony” (“Welcome to the Anthropocene”). This notion should remind us to go forward with caution as to how future civilizations will remember us, who cannot at the present time claim that we did not know the impact that our actions have.