Environmental Science 101: Ecosystems and Biodiversity - Biodiversity Genetic Species Ecosystem Diversity Species Richness vs. Evenness

What This Is

Biodiversity is the variety of life on Earth, encompassing genetic, species, and ecosystem diversity. It matters because biodiversity underpins ecosystem services, such as pollination, pest control, and nutrient cycling, which are essential for human well-being and economic stability. For example, the collapse of pollinator populations due to habitat loss and pesticide use threatens global food production, as seen in the decline of bee populations in the United States.

Key Concepts, Laws & Models

• Species Richness: The number of different species in a given area or ecosystem – explains why tropical rainforests have the highest biodiversity on the planet.
• Species Evenness: The distribution of individuals among species – highlights why some ecosystems, like coral reefs, have a high evenness of species composition.
• Genetic Diversity: The variety of genes within a species or population – underpins the ability of species to adapt to changing environments and resist disease.
• Ecosystem Diversity: The variety of ecosystems, such as forests, grasslands, and deserts – explains why preserving a range of ecosystems is crucial for maintaining global biodiversity.
• Island Biogeography (MacArthur & Wilson): The theory that island size and distance from the mainland determine species richness and extinction rates – has been used to inform conservation efforts, such as the creation of wildlife reserves.
• Species-Area Relationship (SAR): The positive correlation between species richness and area size – helps predict species richness in different ecosystems and informs conservation planning.
• Biodiversity Hotspots (Myers et al.): Regions with exceptionally high levels of endemism (species found nowhere else) and high levels of threat – highlights the importance of preserving areas like Madagascar and the Galapagos Islands.
• The Red Queen Hypothesis (Van Valen): The idea that species must constantly adapt to changing environments to survive – explains why species with high genetic diversity are more likely to persist in the face of environmental change.
• The Precautionary Principle: The idea that we should take action to prevent harm to the environment, even if the evidence is not yet conclusive – underpins many environmental policies, such as the ban on DDT.

Step-by-Step Application

1. Calculate the species richness of a given ecosystem by counting the number of different species present.
2. Evaluate the evenness of species composition in a given ecosystem by calculating the Shannon index or Simpson index.
3. Assess the genetic diversity of a species by analyzing genetic data, such as DNA sequences or microsatellites.
4. Predict the impact of climate change on a given ecosystem by using models, such as the IPCC's climate change scenarios.
5. Evaluate the effectiveness of a conservation effort by measuring changes in species richness, evenness, and genetic diversity over time.

Common Misconceptions

• Misconception: "All pollutants are visible."
• Correction: Many pollutants, such as particulate matter and ozone, are invisible but still pose significant health risks. For example, the 2019-2020 Australian bushfires released massive amounts of particulate matter into the atmosphere, causing widespread air quality issues.
• Misconception: "Renewable energy has no environmental impact."
• Correction: While renewable energy sources, such as solar and wind power, have lower environmental impacts than fossil fuels, they still require land, materials, and infrastructure, which can have environmental consequences. For example, large-scale solar farms can disrupt habitats and affect local ecosystems.
• Misconception: "Biodiversity is only important for ecosystem services."
• Correction: Biodiversity is also important for its intrinsic value, as well as its role in maintaining ecosystem resilience and adaptability to environmental change.

Exam / Free-Response Tips

• Be careful of multiple-choice traps that ask you to choose between two incorrect options, such as "weather vs climate" or "primary vs secondary succession."
• When writing a free-response question (FRQ), make sure to address all parts of the question and provide clear, concise answers.
• When writing a document-based question (DBQ), make sure to use relevant evidence from the provided documents to support your answer.
• Be careful of tricky distinctions, such as "bioaccumulation vs biomagnification" or "endangered vs threatened species."

Quick Practice Scenario

A farmer applies excessive nitrogen fertilizer to their crops, causing a nearby lake to experience an algal bloom. Which nutrient cycle is disrupted, and what secondary effect will deplete oxygen?

Answer: The nitrogen cycle is disrupted, leading to an overabundance of nitrogen in the lake, which will stimulate the growth of algae. As the algae die and decompose, they will consume oxygen in the lake, leading to hypoxia (low oxygen levels).

Last-Minute Cram Sheet

• "El Niño" is not the same as "La Niña" – El Niño is warm phase; La Niña is cool phase, and both are part of the ENSO cycle.
• The Red Queen Hypothesis explains why species with high genetic diversity are more likely to persist in the face of environmental change.
• Biodiversity hotspots are regions with exceptionally high levels of endemism and high levels of threat.
• The Precautionary Principle underpins many environmental policies, such as the ban on DDT.
• Species-area relationship (SAR) predicts species richness in different ecosystems and informs conservation planning.
• Island biogeography (MacArthur & Wilson) explains why island size and distance from the mainland determine species richness and extinction rates.
• The Red List of Threatened Species is maintained by the International Union for Conservation of Nature (IUCN).
• The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) regulates the trade of endangered species.
• The Montreal Protocol phased out the production of ozone-depleting substances, such as CFCs.
• The Paris Agreement aims to limit global warming to well below 2°C and pursue efforts to limit it to 1.5°C above pre-industrial levels.