How Diversity Influences Resiliency

1. How many species can you find in this intertidal community?

Hoonah’s lands and waters are productive natural systems that are critical to subsistence lifestyles. From abundant deer to salmon, berries and other plants and animals, you never have to be hungry in the forest or on the coast if you pay attention to the natural resources around us. People who know and love Hoonah are usually familiar with its diverse subsistence foods – if an area is diverse the same patch of land can provide many different services throughout the year.

forest diversity.jpg
2. A healthy riparian forest has a mixture of different trees, shrubs, sun exposure, nutrients, water flow, and more.

Diversity in nature is important because it provides for Hoonah residents in several ways. It allows us to subsist off the land year-round and it preserves traditional culture. Therefore, it’s important to ensure that these resources are resilient, or able to quickly and effectively recover from harmful events, so that they can provide for generations to come. Respecting and honoring nature also ensures that the plants and animals that we use for subsistence and cultural practices are resilient and long-lasting. Although we can practice sustainable resource management to help guarantee these resources will last, the amount of diversity (a lot of variety in the plants and animals in an ecosystem) present can heavily influence an ecosystem’s resilience. Diversity makes an ecosystem more resilient by increasing the ways the community can address a disturbance and recover more quickly.

genetic diversity
3. Genetic diversity within a limpet population can cause them to look different.

Diversity can take many forms within a system. In ecology they are categorized in three different ways: genetic, species, and ecological diversity. At the smallest scale is genetic diversity which is diversity within a species’ population. For example, a genetically diverse population of fish might include a species of fish that can either be a more shimmery silver or a darker blue. The differences in these fish’s genomes, or genetic makeups, adds diversity to the population and offers better chances to adapt to different situations. Bright silver fish would be more visible to bears against a riverbed full of dark rocks, causing the dark blue fish to have an advantage and survive in this situation whereas the bright silver fish might not. On the other hand, shiny silver fish could have the advantage over dark blue fish if the riverbed consisted of white or grey rocks since the dark blue fish would be more visible to predators. Can you think of ways that salmon are genetically diverse? What other variations have you seen?

Generally there is more genetic diversity when there is a larger population size of a species because there are more organisms that have various genetic makeups. This is often referred to as relative species abundance, or the number of organisms per species in an ecosystem. Here in SE Alaska, there are more genetically diverse populations of juvenile Coho salmon in larger, older streams, emphasizing our need to conserve these historically productive stream systems (Scribner et al., 2003). Genetic diversity within a population gives it a better chance of survival because the individuals could be well suited for a variety of circumstances, making the whole population more resilient if a disturbance occurs.

species diversity
4. Comparison of a forest that is more diverse, Community 1, and of one that is less diverse, Community 2.

Zooming out from the genetic level, species diversity within an ecosystem also contributes to resilience on a bigger scale. The number of species within a given area is referred to as species richness. With more species filling more roles in the system, there would be a better chance of the ecosystem’s survival if one species got wiped out. Spruce beetles are insects that spread quickly and easily devour several species of spruce trees. They are very common and detrimental to forests throughout the United States, for example roughly 40% of Colorado’s spruce-fir forest ecosystems have been affected by spruce beetles since 2000 (Colorado State Forest Service, 2019). In a forest that consists of predominantly spruce trees, spruce beetles could spread from spruce tree to spruce tree and essentially wipe out the whole forest. On the other hand, in a forest that has an even mixture of spruce trees and perhaps western hemlocks, western red cedar, and white birch, spruce beetles would not be able to destroy the whole forest. Other trees that spruce beetles don’t consume would still stand, even if they ate all the spruce trees. This may be the case for the forests around Hoonah even if Spruce Beetles did arrive here. A diverse forest with many different species would be more resilient because there would still be trees present to make up the forest if one tree species was wiped out. Species diversity reinforces an ecosystem’s resilience by providing multiple species to perform the same function, allowing the ecosystem to recover more quickly in the event of a disturbance.

diversity at False Bay
5. You can see the transition between biological communities, or ecotones, along the rocks at False Bay.

On an even greater scale, there are variations of ecosystems found in a region that contribute to a system’s resilience, known as ecological diversity. Anyone living in Hoonah long enough has probably recognized the ecosystem diversity here before, maybe without even knowing that they know it. If you walk from the beach and into the forest you can note the distinct ecosystems and the transition between them such as walking from a beach, through a muskeg, into young growth, and then into old growth. Each of these ecosystems has different plant communities. On the beach, you will find coastal flora like seaweed, kelp, beach asparagus, and seagrass, and the animals you find may include cockles, clams, barnacles, and blue mussels. As you walk into the forest you will realize there are not any of those species. Instead you will see standing spruces or hemlocks covered in witch’s hair or old man’s beard, and the ground will be covered in deer’s heart. Instead of marine animals you’ll perhaps notice squirrels, black-tailed deer, chickadees and thrush. Different ecosystems consist of different biotic and abiotic factors, which could include plants, animals, soil composition, exposure to rainfall, sunlight, or wind, available nutrients, or bacteria. As a result, different ecosystems play different roles and interact with each other. Coastal ecosystems act as water filters whereas forests hold carbon in trees and provide structure for animals we like to eat. Various ecosystems are beneficial because they produce different services that we rely on, adding resiliency to the entire region. How does ecological diversity impact your subsistence harvests? Can you imagine how each of these ecosystems is important to you and your family?

alpine diversity
6. The upper montane forests look different than the forests at sea level. What major differences can you identify?

Maintaining and increasing diversity in an ecosystem or region helps reassure that those resources will continue to grow and thrive, even after facing a harmful disturbance. This is important for Hoonah since we rely directly on these resources and ecosystem services. We also appreciate and celebrate the cultural significance of them, and recognize that these resources and systems have intrinsic value in and of themselves. With climate change comes several unknown consequences, therefore it’s more important now than ever to make sure the resources we depend on are resilient. Additionally, the marine systems in SE Alaska are species depauperate, meaning there isn’t a large quantity or variety of species present, so the relative importance of each species in the ecosystem is greater. Thankfully, Hoonah Indian Association is actively preserving and promoting diversity and resilience by studying intertidal communities through the Coastal Program and helping to manage your forest’s diversity through the Hoonah Native Forest Partnership. There are many other factors that play into making a resilient system, but allowing diversity to flourish within the environment around us can help alleviate the damage that a harmful event does to our precious natural resources.

PS: There are seven visible species in the first picture, however there are many more we can’t see with the naked eye!

Citations:

  • Scribner, K., Sage, G., Soiseth, C., Thorsteinson, L., Nielsen, J., & Knudsen, E. (2003). Genetic analysis of coho salmon colonization in recently deglaciated streams in Glacier Bay, Alaska (Rep.).
  • Colorado State Forest Service. (2019). Spruce Beetle. Retrieved July 9, 2019, from https://csfs.colostate.edu/forest-management/common-forest-insects-diseases/spruce-bark-beetle/
  • https://socratic.org/questions/how-do-species-richness-and-relative-abundance-of-species-affect-species-diversity

 

Written by Arianna Lapke, AmeriCorps VISTA

 

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