The Homogenization of Urban Macro-systems

*This post is by Rabia Ahmed, a student in Marc's 'Causes and Consequences of Diversity' class.

If you have ever walked along a residential street in the city or suburbs you will notice many similar features in each backyard. Often times personal gardens are representative of peoples’ identities and reflect their membership in the neighbourhood. With the expansion of the urban population, an increasing area is covered by personal yards. While each homeowner views their yard to be small and therefore quite insignificant to the overall ecosystem- aggregated across the country, this area quickly adds up. 

 Despite the expansion of urban ecosystems little research has been devoted to understanding the patterns of ecosystem biodiversity, function and assembly. The findings of a recent paper by Pearse et al. (2018) investigated the extent to which “residential macro-systems” are the same across different US cities. The main focus of the paper was to compare the diversity, composition and structure of cultivated yards to the natural ecosystem in different climates across the US.

The results of the study showed that indeed the phylogenetic and species composition in yards had greater homogenization across regions compared to the corresponding natural ecosystems. There was also evidence of homogenization in vegetation as the tree density in yards remained similar across regions, despite the fact that, due to environmental filters, the tree densities in the different urban climates varied significantly. For example, the natural ecosystems in Salt Lake City and Los Angeles almost had no trees, but the tree density in the yards was well above zero.

Figure 1. The above diagram shows the convex hulls (dashed line) for three species pools: cultivated (orange), spontaneous (blue) and natural (green). The regions are abbreviated, Boston, Baltimore, Los Angeles, Miami, Minneapolis–St. Paul, Phoenix, and Salt Lake City as BOS, BA, LA, MI, MSP, PHX, and SL, respectively. The data shows that cultivated and spontaneous pools are more similar across regions than natural area pools, and in all cases, pools in the same geographical area are more similar than pools across a geographical region.

(Retrieved from Pearse et al. 2018)

Surprisingly, however, it was found that urban vegetation whether directly planted or spontaneously growing in the yards, had greater species richness than the comparative natural areas. The greatest phylogenetic diversity (MPD) was found within the fully cultivated yards, suggesting that these species would be better suited to future climate stressors due to their evolutionary distinctiveness. This variation in species lineages provides evidence that people prefer to have a variety of plants and flowers in their backyards which are not often found in the species pool.

Overall the data suggests that similarities in land cover and residential structural characteristics lead to a decrease in microclimate divergence at a continental scale.

These results underscore the common human preference for maintaining yards that are aesthetically pleasing and low maintenance. This homogenization has broad implications as it takes effort to keep these ecosystems the same, across forests, deserts and planes. For example, it has been observed that there is little difference between the amount of irrigation and fertilizers used by homeowners in the driest (Phoenix) or the wettest (Miami) cities.

While many argue that urban and suburban habitats do not compare to natural landscapes, recent research shows that they are more biologically diverse than previously assumed. The increased biodiversity is mostly because of the fact that people plant non-native species along with the native species, and artificial maintenance is used to overcome the environmental filter. Therefore, artificially enriched environments such as yards have both positive and negative consequences on the surrounding environment. For instance, researchers at Boston University found that trees in urban yards grow twice as fast as those in nearby forests, and store carbon at a faster rate. On the other hand, it was found that the rich mulched soils in suburban yards emitted twice as much CO2 as the soil in rural forests.

In conclusion, although yards have been given diminished importance in the study of human-dominated environments, they can provide great insight into how we can make our communities more sustainable. Residents, municipalities and neighbourhood associations can help reshape their residential macro-system into a thriving eco-system one backyard at a time. The key is to keep a balance between human preferences and other organisms’ needs, thus designing landscapes that are not only aesthetically pleasing but also support pollinators and birds.

References

Groffman, Peter M., et al. “Satisfaction, water and fertilizer use in the American residential macrosystem.” Environment Research Letters, vol.11, 29 Feb. 2016, doi:10.1088/1748-9326/11/3/034004

Humphries, Courtney. “The Residential Macrosystem.” Anthropocene, 21 June 2017, www.anthropocenemagazine.org/2017/06/residential-macrosystem-backyard-science/.

Pearse, William D., et al. “Homogenization of Plant Diversity, Composition, and Structure in North American Urban Yards.” Ecosphere, vol. 9, no. 2, 15 Feb. 2018, doi:10.1002/ecs2.2105.

Larval fish nurseries are facing a tiny, yet dangerous new enemy: Microplastics

*This post is by Alexa Torres, a student in Marc's 'Causes and Consequences of Diversity' class.

Recent research has shown that many larval fish species from various ocean habitats are ingesting large quantities of microplastics within their preferred nursery habitat.

Approximately 300 million tons of plastic gets manufactured per year, with around 5 to 13 million tons of it ending up in our oceans. Much of this is in “macro” form such as plastic packaging, fishing nets, and buoys that are quite easy to spot littering shorelines or swirling around the enormous circular currents of the world's oceans. Microplastics constitute pieces of plastic too small in size to be filtered out of sewage systems: synthetic fibers,  microbeads commonly used in cosmetics and industrial cleaners, as well as minuscule scraps that are broken off from any type of plastic. 

Polyethylene beads extracted from cosmetic products, as shown in an electron micrograph, regularly pass through sewage and treatment plant filters, later ending up in open waters.

Image courtesy of Adil Bakir and Richard Thompson (Plymouth University, UK)

A growing number of research as of late have been dedicated to investigating precisely where microplastics are found and their effects on marine life. While much  evidence has shown that adult fish are ingesting plastic, recent studies show that fish at their larval stage are also consuming plastics, as early as mere days after they have been spawned. Larval fish make up the next generation of adult fish of who will supply resources of protein and nutrients to populations around the world, yet little is understood as to the ocean processes that affect the survival of these quintessential organisms.

Surface slicks are naturally occurring, ribbon-like, smooth patches of water on the ocean surface. These water features typically contain high densities of larval fish as well as aggregate plankton, which are an important food source for them. In addition, surface slick nurseries concentrate lots of planktonic prey, providing an oasis of food that is critical for the development and survival for fish in their larval stages. However,  NOAA’s Pacific Islands Fisheries Science Center and an international team of scientists conducted a field study sampling coastal waters of Hawaii and discovered that the same ocean processes that were allowing for the aggregation of prey for larval fish also concentrated passively floating microplastics. “We were shocked to find that so many of our samples were dominated by plastics,” said study co-lead Dr. Jonathan Whitney, a marine ecologist for the Joint Institute for Marine and Atmospheric Research and NOAA. Plenty of times, plastics found in surface sinks, and therefore larval fish nurseries, can be on average eight times higher than plastic densities found in other ocean habitats.

Larval fish lay a foundation to ecosystem function, representing the future of adult fish populations. These organisms are highly sensitive to environmental and food changes. With nurseries and larval fish populations being surrounded by and ingesting toxin-laden plastics that provide no nutrition at their utmost vulnerable life-history stage, it indicates a call for attention and cause for alarm. Plastics ingested by adult fish induce malnutrition, stemming from gut blockages and accumulation of toxins. As a more unfamiliar subject, researchers are not fully aware of the exact harm plastics cause to larval fish, however, they can predict that microplastics may play a role in negative impacts to development and even reduce survivorship of those that ingest them.

Despite calls for classification of plastics to be categorized as hazardous, there has been a lack of legislation to restrict marine debris accumulation as it is still hindered by a lack of evidence to show the exact ecological harm caused. The productivity of fisheries, as well as overall marine biodiversity, are currently threatened by a large number of anthropogenic stressors including climate change, habitat destruction, and overfishing. Modern studies have suggested that pollution of microplastics to fish nurseries and ingestion of them at larval stages are now emerging as a novel issue and have since become the lists’ newest addition.

References

Galloway, T., & Lewis, C. (2016). Marine microplastics spell big problems for future generations. Proceedings of the National Academy of Sciences of the United States of America, 113(9), 2331-2333. Retrieved February 19, 2020, from www.jstor.org/stable/26468516

Katsnelson, A. (2015). News Feature: Microplastics present pollution puzzle: Tiny particles of plastic are awash in the oceans—but how are they affecting marine life? Proceedings of the National Academy of Sciences of the United States of America,112(18), 5547-5549.

Rochman, C., Browne, M., Underwood, A., Van Franeker, J., Thompson, R., & Amaral-Zettler, L. (2016). The ecological impacts of marine debris: Unraveling the demonstrated evidence from what is perceived. Ecology, 97(2), 302-312. Retrieved February 19, 2020, from www.jstor.org/stable/24703091

University of Hawaii at Manoa. (2019, November 11). Prey-size plastics are invading larval fish nurseries. ScienceDaily. Retrieved February 17, 2020 from www.sciencedaily.com/releases/2019/11/191111150636.htm

The “man” in mangroves: How does the Anthropocene impact biodiversity in these ecosystems?

 *This post is by Nina Adamo, a student in Marc's 'Causes and COnsequences of Diversity' class.

Mangroves are among the most biologically important forest ecosystems on Earth, found in the intertidal zone between land and sea along tropical and subtropical coasts around the world.⁷ Mangrove ecosystems provide habitat for a wide range of terrestrial as well as aquatic organisms including plants, fish, mollusks, birds, reptiles, and crustaceans, among many others.¹

Mangroves also serve as nursery habitats for various fish and crab species found in coastal regions, as mangroves provide high abundances of food and shelter for developing wildlife living in coastal regions.⁷ Since many species use mangroves as nursery grounds, fish diversity and abundance in neighbouring coastal ecosystems has been positively linked to the proximity of mangrove areas, suggesting that mangrove habitat is critical in supporting biodiversity in surrounding coastal ecosystems.⁵

Figure 1: Many species such as fish and crustaceans use mangroves as a nursery site for their young, where shelter from predators and food is abundant.⁹

Along with supporting a wide range of biodiversity along coastal ecosystems, mangroves also provide many essential ecosystem services to humans. Some of these societal benefits include natural resources such as fish and timber, coastal protection from storms, and assisting in mitigating climate change by removing carbon dioxide from the atmosphere and storing it.¹¹

Despite the critical role mangroves play in supporting coastal biodiversity and providing ecosystem services to society, mangroves have been disappearing globally at an alarming rate of 1-2% per year due to anthropogenic activities and accelerated global climate change.⁴ The main threats to these ecosystems are rising sea levels causing coastal erosion, environmental condition changes due to climate change, land-use changes, deforestation, and overexploitation of natural resources.⁴ This has led to the loss of about 50% of mangrove coverage across the globe since 1950.¹⁰

In recent years, there have been a great number of studies that have explored the impacts of anthropogenic activities and climate change on the biodiversity of vegetation, benthic meiofauna, and benthic fauna found in mangrove ecosystems.

Figure 2: A stilt mangrove tree in a mangrove forest coastal ecosystem on an island in East Kalimantan, Indonesia.⁸

In the Sundarbans, which is the world’s largest remaining natural mangrove ecosystem located on the border of Bangladesh and India, there has been a homogenization of tree species composition over the span of 28 years from the 1980s to the 2010s.¹⁰ In other words, the largest remaining mangrove ecosystem has experienced a loss in community biodiversity of mangrove plant species over time due to anthropogenic activities and the environmental impact of climate change.

The loss of biodiversity in ecosystems is a crucial issue because higher biodiversity in most ecosystems typically leads to higher ecosystem functioning, so if biodiversity is lost through stressors such as habitat loss or extreme environmental conditions such as those produced through global climate change, it could have severe impacts on the diversity of an ecosystem and hence the functioning of the ecosystem as a whole.²

The biodiversity of benthic meiofauna, which are very small invertebrates that live in the bottom of aquatic mangrove ecosystems, are also negatively impacted by anthropogenic disturbances. In a comparison study of disturbed and undisturbed mangrove areas, disturbed areas displayed a 20% loss of benthic meiofauna biodiversity compared to undisturbed mangrove areas.² Since many juvenile fish species that use mangrove ecosystems as nursery grounds rely heavily on meiofauna for food, this loss of biodiversity through anthropogenic causes could cause a reduction in ecosystem functioning not only within mangrove communities but in surrounding coastal ecosystems as well.²

A similar observation is also found with the biodiversity of benthic fauna in mangrove ecosystems in the Philippines, where protected mangrove ecosystems have significantly higher diversity and abundance of crab species than reforested mangrove ecosystems that have been disturbed by humans.¹ This suggests that environmental factors influenced by climate change and human influences in mangrove ecosystems can have a negative impact on the biodiversity of benthic fauna, one of the most dominant groups in these systems, which could impair the overall functioning of the ecosystem.¹

With the increasing loss of mangrove habitat and the biodiversity within it across the globe due to anthropogenic activities and climate change, it is essential that humans intervene with utilizing other paradigms such as the flagship species paradigm to increase mangrove conservation and policies to protect mangrove habitat,¹¹ well-researched and well-managed mangrove planting restoration,⁶ and more research on innovative manmade artificial mangroves that may help to restore these ecosystems.³

Figure 3: Locations of the various megafauna found in mangroves (locations of mangrove areas shown in green) around the globe, with the orange representing terrestrial and the blue representing aquatic megafauna. Some examples of megafauna found in mangroves (from top-left to bottom-left in a clockwise direction) include the Key deer, Manatee, Sailfin lizard, Sawfish, Three-toed sloth, Spotted deer, Bengal tiger, Otter, Green turtle, Crocodile, and the Proboscis monkey.¹¹

The focus of much of the recent research on mangrove conservation has utilized an ecosystem services approach, where the benefits that mangroves provide to humans is stressed as an incentive for conservation.¹¹ For this reason, most of the research has been focused on smaller benthic invertebrates such as crabs and shrimp, rather than larger charismatic megafauna that are found in mangroves around the world such as sloths, Bengal tigers, green turtles, and proboscis monkeys.¹¹

Conservation awareness of mangrove ecosystems could be improved by using the flagship species paradigm which uses larger charismatic species found in mangrove ecosystems in marketing campaigns that would protect the entire ecosystem in which they are found. Since charismatic megafauna have been observed in mangrove habitats across the globe, using the flagship species paradigm in conjunction with the ecosystem services paradigm could increase public awareness of the threats facing these extremely diverse and productive ecosystems.¹¹

Conserving mangrove ecosystems around the world is important as these ecosystems provide ecosystem services to human society and play a critical role in supporting biodiversity within mangrove systems and in neighbouring coastal systems. With the increasing threat of anthropogenic activities and global climate change, the conservation and protection of mangroves is essential to reduce the decline in ecosystem functioning and biodiversity in these ecologically important ecosystems that many animals and humans alike rely on in order to live productive and successful lives.

References

1.     Bandibas, M. B., & Hilomen, V. V. (2016). Crab biodiversity under different management schemes of mangrove ecosystems. Global Journal of Environmental Science and Management, 2(1), 19–30. https://doi.org/10.7508/gjesm.2016.01.003

2.     Carugati, L., Gatto, B., Rastelli, E., Lo Martire, M., Coral, C., Greco, S., & Danovaro, R. (2018). Impact of mangrove forests degradation on biodiversity and ecosystem functioning. Scientific Reports, 8(1), 1–11. https://doi.org/10.1038/s41598-018-31683-0

3.     Florida Atlantic University. (2018). Humanmade mangroves could get to the “root” of the problem for threats to coastal areas. ScienceDaily. Retrieved February 20, 2020, from https://www.sciencedaily.com/releases/2018/08/180829115627.htm

4.     Hapsari, K. A., Jennerjahn, T. C., Lukas, M. C., Karius, V., & Behling, H. (2019). Intertwined effects of climate and land use change on environmental dynamics and carbon accumulation in a mangrove-fringed coastal lagoon in Java, Indonesia. Global Change Biology. https://doi.org/10.1111/gcb.14926

5.     Henderson, C. J., Gilby, B. L., Schlacher, T. A., Connolly, R. M., Sheaves, M., Flint, N., Borland, H. P., & Olds, A. D. (2019). Contrasting effects of mangroves and armoured shorelines on fish assemblages in tropical estuarine seascapes. Ices Journal of Marine Science, 76(4), 1052–1061. https://doi.org/10.1093/icesjms/fsz007

6.     Kodikara, K. A. S., Mukherjee, N., Jayatissa, L. P., Dahdouh‐Guebas, F., & Koedam, N. (2017). Have mangrove restoration projects worked? An in-depth study in Sri Lanka. Restoration Ecology, 25(5), 705–716. https://doi.org/10.1111/rec.12492

7.     Nagelkerken, I., Blaber, S. J. M., Bouillon, S., Green, P., Haywood, M., Kirton, L. G., Meynecke, J.-O., Pawlik, J., Penrose, H. M., Sasekumar, A., & Somerfield, P. J. (2008). The habitat function of mangroves for terrestrial and marine fauna: A review. Aquatic Botany, 89(2), 155–185. https://doi.org/10.1016/j.aquabot.2007.12.007

8.     Rante, A. (2019, December 12). A stilt mangrove tree in a protected area on Semama Island in East Kalimantan. Supertrees: Meet Indonesia’s mangrove, the tree that stores carbon. [Image].Vox. Retrieved February 20, 2020 from https://www.vox.com/2019/12/12/21009910/climate-change-indonesia-mangroves-palm-oil-shrimp-negative-emissions-blue-carbon

9.     Rante, A. (2019, December 12). In the water lapping at mangrove roots, young fish and plankton take refuge from predators. Supertrees: Meet Indonesia’s mangrove, the tree that stores carbon. [Image].Vox. Retrieved February 20, 2020 from https://www.vox.com/2019/12/12/21009910/climate-change-indonesia-mangroves-palm-oil-shrimp-negative-emissions-blue-carbon

10.  Sarker, S. K., Matthiopoulos, J., Mitchell, S. N., Ahmed, Z. U., Mamun, Md. B. A., & Reeve, R. (2019). 1980s–2010s: The world’s largest mangrove ecosystem is becoming homogeneous. Biological Conservation, 236, 79–91. https://doi.org/10.1016/j.biocon.2019.05.011

11.  Thompson, B. S., & Rog, S. M. (2019). Beyond ecosystem services: Using charismatic megafauna as flagship species for mangrove forest conservation. Environmental Science & Policy, 102, 9–17. https://doi.org/10.1016/j.envsci.2019.09.009

Intellectual death by a thousand cuts

My business is thinking. Let me be a little less succinct. My profession as a Professor of Biology is my passion, and I am fortunate enough to be paid to think about how the natural world works and to come up with possible solutions to global problems. I was trained to do this and my past training (all 11 years) and my current salary are paid by taxpayers to do this. This all seems rather straightforward, but yet why does it feel like the universe is conspiring to prevent this intellectual work from being done?

As pointed out brilliantly by Cal Newport in the Chronicle of Higher Education, in an article titled “Is E-mail Making Professors Stupid?”, Professors are being buried under a pile of administrative work at the expense of intellectual pursuits. The amount of time and effort spent on managing people and money, sitting on departmental/university committees, representing the university externally, and applying for research funds and awards have all increased significantly over time. Professors are increasingly being converted into middle managers, the victims of a culture of bureaucratization and downloading.

At the organizational level, this all makes sense. The necessary regulatory obligations and internal checks and balances are very robust, and appear, to outside scrutiny, as though tax-payer funds are being used correctly and efficiently. However, the reality is that university bureaucracies have grown substantially over the past couple of decades while student enrollment and faculty numbers at many institutions has been stagnant or even declining. And a byproduct of this increased bureaucracy has been an increase in internal programs and procedures that require communication and paperwork.

This increase in internal communication and administration has been paired with increasing external demands for professors’ time. Increasing requests to perform grant and manuscript reviews, participate in panels, pressure to include outreach and knowledge mobilization in research projects, and the inundation of predatory journals and conference requests have been experienced by all researchers.

All these forces conspire to eat away at the ability for professors to do the thing they are actually paid to do –literally the death of the intellectual by a thousand cuts. If I were to properly answer all of the e-mails I receive, I would be spending 3+ hours a day doing this one task. Not to mention meetings. Professors spend much more of their time in meetings today than a generation ago. I just looked at the next week in my calendar (an uneventful week by my standards), and there are 14 hours of meetings scheduled. I also need to schedule these meetings myself an increasingly frustrating activity that requires multiple attempts. So e-mail and meetings alone would amount to about 25-32 hours a week.

 

What should I be doing with my time? Well, working on manuscripts (my students and my own), editing and reviewing for journals, writing grant proposals, teaching, participating in student committees, data analyses, research projects and training, and reading are all necessary. My estimation of the time needed to optimize these, or at least do a minimally acceptable job, would be about 30 hours a week. So, either I work a minimum of 60 hours a week, or something has to give. I am fortunate that I have the resources to hire a lab manager and do not need to deal with lab management and ordering supplies, etc., which would require an additional 4-8 hours a week.

At the moment I am faced with a dichotomous decision, work evenings and weekends or purposefully prioritize certain activities over others. And to the frustration of colleagues and administrators, e-mail tends to the bottom of the priority list. But this cost of bureaucratization should not be burdened by professors alone.

Cal Newport highlights several mechanisms to relieve this burden in his article. Minimally, professors should schedule e-mail time, like one hour a day. And, filed under “do as I say, not as I do”, professors should say 'no' to many of the unsolicited requests that pull them away from their core responsibilities. Yet institutions have a role to play. Newport suggests that Professors require executive assistants to manage e-mail correspondence, scheduling and paperwork and these should come with their positions (not one to one, perhaps shared amongst groups of faculty). Since professors routinely work extra hours to stay on top of all the demands, they should start to be compensated for this additional work. Further, there should be an agreed upon fixed amount of administrative service they are required to do (e.g., 10 hours a week), and going beyond this should require teaching buyouts or other forms of compensation (e.g., funds for assistant).

While the onslaught of demands seems so overwhelming, there are solutions. They just need to be pursued and pushed to university administrations.