An orange zebrafish with black stripes with a neon green aquatic plant.
Figure 1. Newly discovered zebra-striped Eirmotus insignis in Borneo, Southeast Asia.[2]

Overview

Biodiversity is the heterogeneity of all Earth’s life forms: plants, animals, fungi, and microorganisms. There are significant links between biodiversity and ecosystem stability, as it fosters resilience necessary to withstand natural disaster, habitat destruction, human development, and climate change.[1]

As humans continue to exploit the planet’s resources, biodiversity suffers. According to the World Wildlife Fund’s 2018 Living Planet Report, there has been an average decline of 60% in the global species populations of mammals, fish, birds, reptiles, and amphibians since 1970.[3] The preservation of biodiversity on Earth is not only beneficial to wildlife but also to humans. Maintaining biodiversity increases the availability and stability of food, clean water, medicine, and shelter.[4]


Metrics

To assess the biodiversity of populations within the scope of urban greenification, the Terrascope Class of 2024 project utilizes four criteria: taxonomic diversity, genetic diversity, ecosystem diversity, and endemic species concentration because of their relevance to urban settings. These criteria are defined in more depth below. Biodiversity loss describes the decline of numbers, genetic variation, and species in a habitat, leading to a breakdown of the ecosystem and its surroundings. Scientists have warned that humans are entering the sixth mass extinction—nearly 60% of U.S. native vegetation and more than 500 animal species have been lost. Habitat degradation and other causes of biodiversity loss cost the global economy between USD 4-11 trillion per year from 1997 to 2011 in ecosystem services, as well as indirect costs in food waste and tourism.[5]

Taxonomic Diversity and Distinctness

A phylogenetic tree of vertebrates, showing a clade diagram connecting different species.
Figure 2. A simplified phylogenetic, tree of vertebrates.[12].

Taxonomic diversity and distinctness are both measures of the taxonomic relatedness of a population.[6],[7] They utilize the path length, or “distance”, between individuals on a phylogenetic tree. Through this analysis, organisms that share a recent common ancestor would have a shorter distance between them on the tree.

Taxonomic diversity (Δ) is the average (weighted) distance between all pairs of individuals within a population.[8]Taxonomic distinctness*) is a similar measurement; it is the average (weighted) distance between all pairs of species in a population.[9] The main difference in calculation is that taxonomic distinctness ignores the paths between individuals of the same species. In practice, taxonomic diversity is a metric that includes aspects of taxonomic relatedness and evenness, whereas taxonomic distinctness is simply a measure of pure taxonomic relatedness.[10]

Taxonomic diversity and taxonomic distinctness are useful metrics of biodiversity because they go beyond the traditional species-oriented perspective of biodiversity by incorporating higher taxonomic ranks in their analysis.[11]

On the top, the formula for taxonomic diversity, defined as Δ. On the bottom, the formula for taxonomic distinctness, defined as Δ*.
Figure 3. The formulae for Clarke and Warwick’s taxonomic diversity index (top) and their taxonomic distinctness index (bottom).[14] For a full explanation of the calculations, click on the citation to visit Clarke and Warwick’s published work.

Additionally, both metrics appear to be less sample-size dependent than other common diversity measures, such as species richness and evenness.[13] To quantify these metrics, Clarke and Warwick’s taxonomic indices can be used (shown in Figure 3).


Genetic Diversity

Genetic diversity describes the genetic variability within species.[15] It is significant because increased genetic diversity can make a population less vulnerable to external pressures. Having a large gene pool, and thus more phenotypes and possible genetic combinations, increases the likelihood that an individual within that population will be resistant to significant change.[16] A functional example of this is a disease that affects certain individuals in a population. If each individual within a population were a clone, with identical genetic makeup, they would equally be susceptible to this disease. The entire population would be wiped out because of this shared vulnerability. However, increased genetic diversity would prevent a similar catastrophic event. This is because individuals within the population all have slightly different genetic makeup, decreasing the likelihood that the population has a common vulnerability.

This phenomenon of an extinction event is actually what happened to the Gros Michel strain of bananas in the 1950’s, since each tree was a clone of the other.[17]

Species Diversity


2 boxes, each with 25 total shapes and 5 different shape types. Box A has mostly circles, while box B has five of each type.
Figure 4. Both communities contain five “species” of shapes, so species richness is the same. The community on the left is dominated by one of the species, while the community on the right has equal proportions of each. The community on the right has higher species diversity, because evenness is higher.[23]


Species diversity can be quantified in several ways, but Terrascope Class of 2024 defines species diversity as a measure of the species richness and evenness of a population. Species richness is a basic count of the number of species in a community, without regard for the relative distributions of species throughout an area.[18] Species evenness measures the proportions of abundance between species. Evenness is higher when species are present in similar proportions.[19] These concepts are visually explained in Figure 4.

Species richness-evenness can be quantified using indices. A commonly used index within ecological literature is the Shannon diversity index.[20] Assumptions made for calculation are that individuals were randomly sampled from a large population, and all species are represented in this sample.[21],[22]

Endemic Species Concentration

Endemic species are species that are unique to a defined geographic area.[24] Measuring the relative abundance of endemic species to the rest of the population is an effective tool, because it provides insight to the biodiversity of the region as a whole.[25] This is due to the fact that the loss of endemic species often causes a global loss of species diversity—if there is a low concentration of endemic species within a region, it becomes more similar to surrounding regions, which would decrease biodiversity overall.[26]


Conclusion

After assessing the four criteria detailed above, Terrascope Class of 2024 chose to address biodiversity through the lens of urban greenification. This website presents a proposal to promote biodiversity urban spaces through adding, improving, and maintaining various green spaces within and around cities. The proposal is divided into three sections: reducing the harmful impacts of urban sprawl, introducing adaptive landscaping, and implementing alternative agricultural methods.

 


[1] Cleland, E. E. (2011). Biodiversity and ecosystem stability. Nature Education Knowledge, 3(10). https://www.nature.com/scitable/knowledge/library/biodiversity-and-ecosystem-stability-17059965/ 

[2] WWF. (n.d.). Borneo Wildlife. Retrieved November 17, 2020, from https://wwf.panda.org/knowledge_hub/where_we_work/borneo_forests/about_borneo_forests/borneo_animals/

[3] WWF. (2018). Living planet report 2018: Aiming higher (M. Grooten & R. E. A. Almond, Eds.). https://www.wwf.org.uk/sites/default/files/2018-10/LPR2018_Full%20Report.pdf 

[4] Hancock, L. (n.d.). What is biodiversity? World Wildlife. Retrieved November 13, 2020, from https://www.worldwildlife.org/pages/what-is-biodiversity 

[5] OECD. (2019). Biodiversity: Finance and the Economic and Business Case for Action, report prepared for the G7 Environment Ministers’ Meeting, 5-6 May 2019. https://www.oecd.org/environment/resources/biodiversity/Executive-Summary-and-Synthesis-Biodiversity-Finance-and-the-Economic-and-Business-Case-for-Action.pdf

[6] Braun, A. (2015) Taxonomic Diversity and Taxonomic Dominance: The Example of Forest Plantations in South-Central Chile. Open Journal of Ecology, 5, 199-212. https://www.scirp.org/journal/paperinformation.aspx?paperid=56492 

[7] Clarke, K. R. & Warwick, R. M. (1999). The taxonomic distinctness measure of biodiversity: Weighting of step lengths between hierarchical levels. Marine Ecology Progress Series, 184, 21-29. https://www.jstor.org/stable/24853226

[8] Clarke, K. R. & Warwick, R. M. (1995). New ‘biodiversity’ measures reveal a decrease in taxonomic distinctness with increasing stress. Marine Ecology Progress Series, 129, 301-305. https://www.int-res.com/articles/meps/129/m129p301.pdf

[9] Ibid.

[10] Sohier, C. (2020). Measurements of biodiversity. http://www.marinespecies.org/introduced/wiki/measurements_of_biodiversity

[11] Mistrim, M., Ceccherelli, V. U., & Rossi, R. (2000). Taxonomic distinctness and diversity measures: Responses in lagoonal macrobenthic communities. Italian Journal of Zoology, 67(3), 297-301. https://doi.org/10.1080/11250000009356327

[12] Yamamoto, K., Bloch, S., & Vernier, P. (2017). New perspective on the regionalization of the anterior forebrain in Osteichthyes. Development Growth and Regeneration, 59(4). https://www.researchgate.net/publication/316690258_New_perspective_on_the_regionalization_of_the_anterior_forebrain_in_Osteichthyes

[13] Clarke, K. R. & Warwick, R. M. (1995). New ‘biodiversity’ measures reveal a decrease in taxonomic distinctness with increasing stress. Marine Ecology Progress Series, 129, 301-305. https://www.int-res.com/articles/meps/129/m129p301.pdf

[14] Ibid.

[15] National Human Genome Research Institute. (n.d.). Gene pool. National Human Genome Research Institute. Retrieved November, 2020, from https://www.genome.gov/genetics-glossary/Gene-Pool 

[16] Ibid.

[17] Thompson, S. (2019, April 18). The quest to save the banana from extinction. The Conversation. https://theconversation.com/the-quest-to-save-the-banana-from-extinction-112256

[18] Tribot, A.-S., Mouquet, N., Villéger, S., Raymond, M., Hoff, F., Boissery, P., Holon, F., & Deter, J. (2016). Taxonomic and functional diversity increase the aesthetic value of coralligenous reefs. Scientific Reports, 6, 34229. https://doi.org/10.1038/srep34229

[19] Pyron, M. (2010) Characterizing Communities. Nature Education Knowledge, 3(10), 39. https://www.nature.com/scitable/knowledge/library/characterizing-communities-13241173/

[20] Sohier, C. (2020). Measurements of biodiversity. http://www.marinespecies.org/introduced/wiki/measurements_of_biodiversity

[21] Ibid.

[22] Beals, M., Gross, L., & Harrell, S. (2000). Diversity indices: Shannon’s H and E. The Institute for Environmental Modeling. http://www.tiem.utk.edu/~gross/bioed/bealsmodules/shannonDI.html

[23] Pyron, M. (2010) Characterizing Communities. Nature Education Knowledge, 3(10), 39. https://www.nature.com/scitable/knowledge/library/characterizing-communities-13241173/

[24] Behroozian, M., Ejtehadi, H., Memariani, F., Pierce, S., & Mesdaghi, M. (2020). Are endemic species necessarily ecological specialists? Functional variability and niche differentiation of two threatened Dianthus species in the montane steppes of northeastern Iran. Scientific Reports, 10, 11774. https://doi.org/10.1038/s41598-020-68618-7

[25] National Research Council (US) Committee on Noneconomic and Economic Value of Biodiversity. (1999). Perspectives on biodiversity: Valuing Its role in an everchanging world. National Academies Press. https://www.ncbi.nlm.nih.gov/books/NBK224405/

[26] Ibid.