|This conservation resource was created by Mikhail Din; Justin Mak; Malavan Subramaniam; Sebastian Gomez Montenegro. It is shared under a CC-BY 4.0 International License.|
In his book On the Origin of Species, Charles Darwin went over the theory of evolution by natural selection. Alluding to Thomas Malthus’ principle of exponential population growth, Darwin explained that species must compete for their existence. He argued that what ultimately determines which species survive and prosper are advantageous variations—variations that allow species to adapt to changes in their environment with more ease than other species. In simple terms, the process of natural selection will allow species with advantageous variations to survive and force species without them to become extinct. The point is, extinction is a natural process that has happened since life on Earth began. Today, however, extinction is no longer evolutionary, as anthropogenic activities such as urban expansion are the main driver of the extinction of species. Scientists have referred to this as “biological annihilation” and some even think overpopulation and overconsumption are pushing the Earth to its sixth mass extinction . Our planet is an ecosystem. It can be thought of as an interconnected network, where every species relies on the contributions of other species. Because of this, protecting critically endangered species should be a priority.
The International Union for Conservation of Nature (IUCN), is a membership union composed by governmental bodies and civil society organizations with the purpose of enabling human progress, economic development and conservation to occur simultaneously . The IUCN strives to provide the necessary assistance and resources to public, private and non-governmental organizations to make this happen. It’s Red List of Threatened Species is “the most comprehensive, objective global approach” for evaluating the conservation status of species of plants and animals worldwide. As of 2017, 25,821 was the estimated number of threatened (Critically Endangered (CR), Endangered (EN), or Vulnerable (VU)) species . Approximately, 22% of these species are classified as CR. Three of them will be studied in closer detail later on.
Temperate forests, otherwise referred to as deciduous forests, “cover 297 million hectares of North America and represent 41% of the total forest lands in the United States” . These forests are not just ample but also extremely productive. In fact, they are among the most highly productive ecosystems in the world. Additionally, temperate forests also sequester immense amounts of carbon, are a source of clean water, and support high levels of biodiversity. Apart from offering numerous environmental services, temperate forests also offer many economic and social services. For instance, countless forests products can be derived from them, such as timber, and a diverse amount of recreational activities can be held within them, such as hiking and camping.
Temperate forests are also home to many “sensitive plant communities”  that serve as indicators. These communities respond quickly to changes in their surroundings, especially environmental perturbations like climate change and pollution.
As mentioned earlier, the leading cause of the extinction of species today is human activities. Among these, urban expansion has played a major role. Urban expansion, or urban sprawl, is the spreading of urban developments from populated areas to more rural or undeveloped lands. It can simply be defined as the “flooding of concrete and asphalt” . Human populations and land change are positively correlated. As human populations continue to increase at the fast rate they are doing so, it is expected that the rate of change of land will increase greatly over the next 20-50 years .
Besides directly contributing to the extinction of species through obvious habitat loss and fragmentation, urban expansion in North America also contributes to the extinction of species indirectly because it is an important catalyst of climate change and pollution. As urbanization and agriculture expand, there will be more emissions of pollutants such as nitrogen oxides, ozone, volatile organic compounds, and aerosols . These have detrimental effects not only near their emission source but also kilometers away due to atmospheric chemistry. For instance, nitrogen loading, caused by the emission of nitrogen oxides and their interaction with hydrocarbons in the atmosphere, would negatively affect plant development and ecosystem productivity as tropospheric ozone would be absorbed by leaves. The absorption would degrade the chlorophyll and hinder the process of photosynthesis. This is not the end of the story. If nitrogen loading and other forms of pollution such as ozone exposure continue, nitrates and acids would be introduced to waterways, eutrophication (harmful algal blooms) would occur in the coasts, and nitrogen-demanding species would invade ecosystems.
Another reason why expanding human settlements negatively affect ecosystems is that they significantly change biochemical inputs, flow paths, and exports in areas undergoing development . For example, as a result of urban expansion, hydrologic connections would be redefined. The changes in water delivery and supply systems would ultimately lead to distributions in aquatic ecosystems.
When one understands the effects urban expansion has on ecosystems and their properties, it comes to no surprise that species worldwide are facing the threat of extinction. With the help of the IUCN’s comprehensive Red List, 3 species were identified in North American temperate forests that are critically endangered due to residential and commercial development. These species, their roles and the problems they face will be analyzed at next.
The populations of bumble bees (Bombus spp.) have been declining across the globe for many years. As of 2015, the Rusty-patched Bumble Bee (Bombus affinis) population had decreased so much in North America that the IUCN (International Union for the Conservation of Nature) issued them a critically endangered status. 20 years ago The Rusty-Patched Bumble thrived as a species, spanning across 28 states and provinces. Now, after 2 decades, the Bombus affinis population has decreased by over 90 percent, leaving them on the verge of extinction. These bees are on the larger end of bumblebee species, averaging approximately 2 centimeters long, with the Queen Bees being slightly larger. Like most other bumblebee species, Bombus affinis have a yellow and black body, but the male and worker bees have a rusty-colored patch on their bodies, hence the name Rusty-Patched Bumble Bee.
Bumblebees (not just Bombus affinis) play an extremely important role in our ecosystems. They pollinate approximately 1/3 of all the food we eat around the globe. Around 85% of all crops require bumblebees and other insects to pollinate them. Not only are they important for the human food supply, but many berries and seeds that get consumed by small birds and mammals all stem from plants that have been pollinated by bumblebees. They have co-evolved with flowering plants, as bees need these plants for food and flowering plants need bees to reproduce.
The Rusty-Patched Bumble Bee, while visiting a flower for food, will get covered in pollen that comes from the flower's stamen (male reproductive organ). The pollen will remain on the bumble bees and get deposited on the stigma (female reproductive organ) of the next plant that the bumble visits. Bumblebees (as well as other pollinating insects) tend to stick to the same species of flowers when flying around, which is fortunate for the flowers looking to reproduce.
There are a few major factors linked to the decline of bumblebee populations such as Bombus affinis, including climate change and diseases, but a third problem is Urbanization and development. Studies have shown that urban development and the change in land-use are critical factors in the decline of bee populations. The interesting thing is that this problem mainly affects the female bumble bees due to the differences in foraging techniques, which ultimately causes a problem for bumblebee reproduction and population sizes. When humans start to build out over bumblebee territory, they drastically reduce flowering plant biodiversity as well as limit decent nesting sites (especially for ground nesting species).
Quercus Boyntonii (Boynton Oak) is a rare species of North American Oak, ranging from two to an occasional six meters in height. Its leaves are obovate and have a margin that exhibits 3-5 irregularly shaped lobes. The upper side is shiny and dark green whereas the underside is described as a greyish pubescence. Although a lack of population research, it is believed that the range of the Boynton Oak has narrowed down to the state of Alabama. This follows the recent extirpation of the Texan subpopulation. In Alabama, the species does occupy its natural habitat of sandstone outcrops which are also within a matrix of pine-oak-hickory forest. The occurrences are close enough in proximity that gene flow and exchange can take place. Furthermore, the population is estimated to be approximately 200 individuals in size. However, this count is in decline and given that all remaining individuals are a part of the same subpopulation, the state of this species is of a critical nature.
Aside folklore, oak trees were a source of food for many indigenous groups of North America. Quercus Boyntonii is a member of the white oak group and the acorns of such trees were especially coveted for their sweetness. These acorns are also an important food source for a variety of animals. This includes birds such as jays, pigeons, and some species of woodpeckers as well as smaller mammals like squirrels, mice, and several other rodents. Larger mammals like bears and deer also feed upon acorns. The oak nut is an attractive food source for its high nutritional value. Acorns contain high amounts of carbohydrates, proteins, fats, and minerals like calcium, phosphorus, potassium, and the vitamin niacin. The total food energy available through the oak nut is comparable to other popular wild foods and nuts.
Urban expansion is the most pervasive threat to Q.Boyntonii. One of the outcomes of urbanization is landscape fragmentation which can alter naturally occurring fires. These processes promote the growth and reproduction of the species due the release of nutrients from incinerated materials into the soil. The oak is also threatened by the use of habitat as staging areas for trash dumping, ATV activity, and logging operations (Scholz, A., personal communication, 2010).
Malaxis bayardii, commonly known as Bayard’s Adder’s-Mouth orchid, is an orchid species found in northeastern North America. It is a small plant and features one or two, though rarely, polished leaves. The distribution spans from Massachusetts to North Carolina with outlying subpopulations in Ohio and Nova Scotia as well. There is belief that the species has experienced extirpation in states such as Virginia, West Virginia, New York, and New Jersey. As a result, there is an estimation of 12 sites of occurrence. From the available data, there are between 1 to 5 mature individuals at each of these sites and approximately 50 mature individuals in total. Such population data is a significant indicator of the species’ critically endangered status. The habitat of M.Bayardii varies among states. For example, its habitat in Pennsylvania is either a steep, dry shale or very dry, open woods on hilltops. In Southern New England, the species inhabits sand plains and clearings in comparison to coastal plains from Virginia to Massachusetts. There is also geographic variation in the blooming season of M.Bayardii. For subpopulations in the northern region of the species’ distribution, blooming begins in early July and continues until middle to late August. Peak bloom occurs in late July. As for southern subpopulations, the bloom period spans from July to September with peak bloom occurring as late as September. The flowers are often small and green and can form a raceme of up to 70 flowers. Fruits also appear mid to late summer.
Orchids such as M.Bayardii are often analyzed by perfumers to identify any potential chemicals that can serve as fragrances. Orchids are also coveted for purposes of horticulture and collection. There are numerous organizations around the world that encourage cultivation and collection of orchids but some focus on conservation and research of certain species. Given its critically endangered status and lack of scientific research, M.Bayardii demands the attention of such organizations.
The species is threatened by destructive habitat disturbances that compromise plants or compact and disrupt the soil. Examples of such disturbances are land conversion for development or other anthropogenic land uses, road maintenance, use of off-road vehicles, and mowing during the reproductive period.
As of 2012, the IUCN (International Union for the Conservation of Nature) has identified the Dusky Gopher Frog (Lithobates sevosus) as the most endangered frog species in North America. To really put this into perspective, this species makes an appearance in their top 100 most endangered species list . This species was originally considered to be a subspecies of the gopher frog; however, the U.S. Fish and Wildlife Service has officially elevated the status of the Dusky Gopher Frog to be a full species . Historically found in parts of southwest Alabama, southern Mississippi and southeast Louisiana, the Dusky Gopher Frog goes by many names such as the Mississippi gopher frog (Rana capito sevosa/Rana sevosa), the dusky crawfish frog (Rana aerolata sevosa), and the dark gopher frog (Lithobates sevosa) .
The features that distinguish this frog from other species includes its wartyback that secretes a bitter white substance that is used as a defense mechanism along with ridges going down along it and dark black, brown, and grey spots on its back, chest, and chin . The Dusky Gopher Frog also has a particularly large head and mouth and is known to be between 5.6 – 10.5 cm in size with short, thick limbs and hind feet that lack a lot of webbing around between the toes . Female frogs have been observed to be generally larger than the males.
Frogs play an important role in the balance, health, and diversity of an ecosystem and provide many beneficial services to the natural world and humans as well. Frogs are located in the middle of the food chain and are involved in both predator and prey aspects of an ecosystem. They provide important pest control through the consumption of insects and are also a food source for birds, snakes, and other animals on the food web . Additionally, frogs provide an especially important environmental link to water and land. Free-living tadpoles help tie the aquatic system with the land system in an ecosystem . When dual system species goes extinct, it can be equivalent to losing two species . Frogs have also been involved extensively in medical research. It has been found that chemical compounds found in the skin secretions of frogs can be used for everything from non-addictive painkillers to cancer cures.
The principal threats to the dusky gopher frog include degradation and destruction of breeding and non-breeding habitat, habitat fragmentation, and alteration of hydrological patterns due to the urbanization and climate change . There are several prominent threats that are causing the potential extinction of the dusky gopher frog. The major threats that contribute to this species being listed as critically endangered include population isolation, urbanization, diseases, and a lack of a suitable habitat . The population isolation of the Dusky Gopher Frog is a result of species inbreeding and their unfortunate inability to adapt and recover from catastrophic events such as forest fires. Urbanization and human intervention have significantly reduced the range of the Dusky Gopher Frog through acts of habitat destruction and modification, and fragmentation. The loss and alteration of the Dusky Gopher Frog’s habitat from human activities such as tree logging, agriculture, and grazing is a major contributor to the alarming population decrease. More specifically, the destruction of native longleaf line forests and ephemeral wetlands which serve as breeding grounds for the Dusky Gopher Frog . There is estimated to be less than 250 adult frogs and between 60 to 100 mature adult frogs in the entire population of this species remaining which classifies this species as critically endangered according to the IUCN and makes the species extremely susceptible to extinction. This has resulted in the current range of the species being reduced to just three ponds in the south of Mississippi. These ponds include Glen’s Pond, Mike’s Pond and McCoy’s Pond (Mississippi Species, 2018). Another influence for the rapidly decreasing population is the varied breeding success which has been reduced each year mainly due to breeding ponds drying up before the tadpoles have time to fully mature and develop into adults . Dusky Gopher Frogs have a typical life expectancy of 7 years where males reach biological maturity in about 6 to 8 months and 24 to 36 months for females .
The critically endangered status of the Dusky Gopher Frog has generated an increase in conservancy measures over the last decade in order to protect this species from going extinct. In 2004, a team of biologists began transferring tadpoles and young frogs from Glen’s Pond in Harrison County to an ephemeral wetland in Jackson County with the goal of establishing a new population . An organization called “The Conservancy” is working on the development of ponds that may be potential gopher frog habitats. A population of dusky gopher frogs will be translocated to ponds that are successfully developed and able to support the population .
Throughout this paper, the negative and sometimes irreversible impacts of urban expansion on biodiversity across North American temperate forests have been emphasized. Now, the paper will continue by analyzing some of the best solutions to mitigate the effects the concerning issue.
One solution to urban expansion is to adopt a zero population growth strategy. With no population growth, expansion would not be justified. Although some people might think this would entail negative economic growth, environmentalists and Scandinavian countries have proven otherwise . This solution, however, would be hard to implement as it depends heavily on the state or juncture of a country. Canada, for instance, has recently experienced birth rates below replacement. Immigration is the only reason why the country has achieved positive population growth rates. Because Canada relies so heavily on immigration, it is unlikely that the nation would adopt a zero population growth strategy. This leads us to the second alternative to combat urban expansion.
A more measurable approach was proposed by Dr. Shahab Fazal, a professor at Aligarh Muslim University, India. He suggested that instead of adopting tighter growth controls like a zero population growth strategy, federal governments should look toward strengthening agricultural land conversion laws, as urban expansion “cannot be restricted” . He argues, however, that with proper management and planning, it is possible to “strategically channel outward expansion” onto less fertile lands .
One way urban expansion can be dealt with strategically can be by distributing what he calls land capability maps. These would provide valuable information to city planners of which lands are fertile and which lands are not. These plans would be beneficial especially in third world countries where unplanned expansion happens very frequently, sometimes without supervision. The purpose of land use planning is basically to “integrate the essential use of land” .
The best solution to protect critically endangered species from urban sprawl, however, is called “smart growth” . This alternative was developed by Noel Keough, an assistant professor of environmental design at the University of Calgary. Smart Growth is based on New Urbanism, an urban design movement that is based on the principles of how cities have been constructed for centuries. Aspects of New Urbanism include walkable streets, proximal housing and shopping centers, and accessible public spaces . Smart growth has three components:
The first component of smart growth consists of making it more convenient to ride the bus than one’s own car. In other words, communities must be supported with viable public transportation. As feasible as this may seem on paper, in reality, it is very hard to achieve as “tens of billions in public monies”  would be needed to develop the kind of system that would support the transportation of people and goods in denser cities. The level of investment needed to provide viable public transportation is beyond municipalities. This is an issue federal and provincial governments would have to work around.
The second step in achieving smart growth is to increase density in areas that are already developed. Higher density means more homes (smaller) per unit of land. Apart from mitigating the effects of urban expansion, higher density would also lead to shorter commutes and greater accessibility to facilities such as hospitals, schools and offices to name a few. Higher density does not necessarily require turning cities into skyscraper jungles. In fact, Keough argues that pursuing intensification with 5-8 story buildings would suffice. To increase density in developed establishments, population growth must be fully absorbed by these areas and federal and provincial governments must invest billions in public transit, as mentioned above. It is important to note that such increases in densities are needed as these would “justify the operational costs of major dedicated right-of-way public transit systems” .
The third and final step in achieving smart growth is to create “live/work/play communities”. To do so, communities must become neighborhoods, as Keough put it. People must be able to find jobs, engage in recreational opportunities and prosper within the boundaries of their community. A more walkable and connected city means a more sustainable city.
To conclude, if federal and provincial government strive to provide viable public transportation, increase densities in developed areas and redefine communities by making them networkable, smart growth could be achieved. This would not only prevent urban expansion from spreading to biodiverse, natural lands but also exponentially increase cities’ standard of living. Because of its great benefits, it is the best strategy to combat the growing issue of urban sprawl and protect critically endangered species in North American temperate rainforests.