🌈Earth Systems Science Unit 11 – Terrestrial Biomes and Ecosystems

Key Concepts and Definitions

• Biome refers to a large ecological area on the earth's surface with distinctive plant and animal communities adapted to the region's physical environment
• Ecosystem consists of all the living organisms (biotic factors) in an area and the non-living aspects (abiotic factors) of their environment, interacting as a system
• Biodiversity encompasses the variety of life at all levels of organization, including genetic diversity, species diversity, and ecosystem diversity
• Trophic levels represent the position an organism occupies in a food chain, such as producers (plants), primary consumers (herbivores), secondary consumers (carnivores), and decomposers
  • Energy flows through trophic levels, with only about 10% of energy transferred from one level to the next due to energy loss through metabolic processes and heat
• Biogeochemical cycles describe the movement of essential elements (such as carbon, nitrogen, and water) through the biotic and abiotic components of an ecosystem
• Ecological succession refers to the gradual process by which ecosystems change and develop over time, often following a disturbance
  • Primary succession occurs in areas where no soil exists (rock surfaces or lava flows), while secondary succession takes place in areas where soil remains after a disturbance (abandoned agricultural fields or forest clearings)
• Keystone species play a disproportionately large role in maintaining the structure and function of an ecosystem relative to their abundance (sea otters in kelp forests or wolves in Yellowstone)

Types of Terrestrial Biomes

• Tundra characterized by low temperatures, short growing seasons, and limited precipitation, supporting hardy vegetation like mosses, lichens, and dwarf shrubs (Arctic tundra)
• Boreal forests (taiga) feature coniferous trees adapted to cold temperatures and acidic soils, such as spruces, firs, and pines (Canada and Siberia)
• Temperate forests divided into deciduous and coniferous forests, with distinct seasons and moderate precipitation
  • Deciduous forests have trees that lose their leaves seasonally (maple and oak), while coniferous forests have evergreen trees (pines and firs)
• Temperate grasslands (prairies and steppes) characterized by grasses, herbs, and few trees due to moderate precipitation and frequent fires or grazing (Great Plains of North America)
• Deserts defined by low precipitation and extreme temperatures, supporting drought-resistant plants (cacti and succulents) and animals with adaptations to conserve water (camels and kangaroo rats)
  • Deserts can be hot (Sahara) or cold (Gobi), depending on latitude and elevation
• Tropical rainforests found near the equator, with high temperatures, abundant rainfall, and incredible biodiversity (Amazon and Congo basins)
  • Rainforests have distinct layers: emergent, canopy, understory, and forest floor
• Savanna characterized by grasses, scattered trees, and large herbivores, with seasonal rainfall and frequent fires (African savanna)

Ecosystem Components and Interactions

• Biotic components include all living organisms in an ecosystem, such as producers (plants), consumers (animals), and decomposers (bacteria and fungi)
• Abiotic components consist of non-living factors that influence the ecosystem, such as temperature, precipitation, sunlight, soil type, and topography
• Food webs depict the complex feeding relationships within an ecosystem, connecting producers, consumers, and decomposers through energy transfer
  • Changes in one part of the food web can have cascading effects on other parts of the ecosystem
• Symbiotic relationships occur when two species interact closely, including mutualism (both species benefit), commensalism (one benefits while the other is unaffected), and parasitism (one benefits at the expense of the other)
  • Mutualism: Oxpeckers remove ticks from rhinos, gaining food while improving the rhino's health
  • Commensalism: Barnacles attach to whales for mobility and access to food particles, without harming the whale
  • Parasitism: Mistletoes grow on trees, extracting nutrients and water from the host tree
• Niche refers to an organism's role and position within an ecosystem, including its habitat, diet, and interactions with other species
  • Competitive exclusion principle states that two species with identical niches cannot coexist indefinitely, as one will outcompete the other for resources
• Ecological resilience describes an ecosystem's ability to withstand and recover from disturbances, maintaining its structure and function
  • Resilience is influenced by factors such as biodiversity, functional redundancy (multiple species performing similar roles), and the adaptive capacity of species

Climate's Influence on Biomes

• Temperature and precipitation patterns are the primary determinants of terrestrial biome distribution, shaping the growth and survival of plant and animal communities
• Köppen climate classification system categorizes the world's climates based on temperature and precipitation, with five main climate types: tropical, dry, temperate, continental, and polar
  • Each main climate type is further divided into subtypes based on seasonal variations in temperature and precipitation
• Latitude affects the amount of solar radiation received, with higher latitudes receiving less direct sunlight and experiencing cooler temperatures compared to lower latitudes
• Elevation influences temperature and precipitation, with higher elevations generally experiencing cooler temperatures and increased precipitation due to orographic lift
  • Montane ecosystems demonstrate altitudinal zonation, with distinct biomes occurring at different elevations (e.g., alpine tundra above the tree line)
• Ocean currents can moderate coastal climates, with warm currents (Gulf Stream) bringing heat to higher latitudes and cold currents (California Current) cooling adjacent land masses
• Rainshadow effect occurs when mountain ranges block moisture-laden air, creating drier conditions on the leeward side (e.g., the Great Basin in North America)
• Climate change, driven by anthropogenic greenhouse gas emissions, is altering temperature and precipitation patterns worldwide, leading to shifts in biome distribution and ecosystem functioning
  • Warming temperatures are causing poleward and upslope migrations of species, changes in phenology (timing of life events), and increased frequency and intensity of disturbances like wildfires and droughts

Adaptations of Flora and Fauna

• Adaptations are traits that enhance an organism's survival and reproduction in its environment, shaped by natural selection over generations
• Plant adaptations to arid environments include:
  • Succulent leaves or stems for water storage (cacti)
  • Deep root systems to access groundwater (mesquite)
  • Small, waxy leaves to reduce water loss through transpiration (creosote bush)
  • Photosynthetic stems to minimize surface area for water loss (palo verde)
• Animal adaptations to cold climates include:
  • Thick fur or feathers for insulation (polar bears, penguins)
  • Countercurrent heat exchange in extremities to minimize heat loss (arctic foxes)
  • Hibernation to conserve energy during winter months (ground squirrels)
  • Migratory behavior to escape harsh conditions (arctic terns)
• Camouflage helps organisms blend in with their surroundings, reducing detection by predators or prey (leaf-tailed geckos, arctic hares)
• Mimicry occurs when one species evolves to resemble another, often to deter predators or gain access to resources (viceroy butterflies mimicking monarch butterflies)
• Keystone species adaptations:
  • Beavers' ability to modify their environment by building dams, creating wetland habitats that support diverse species
  • Elephants' large size and dietary preferences, which shape savanna vegetation structure and maintain open grasslands

Human Impact and Conservation

• Habitat loss and fragmentation due to land-use changes (agriculture, urbanization, and resource extraction) are major threats to biodiversity
  • Deforestation in tropical rainforests leads to the loss of unique species and disrupts carbon and water cycles
  • Grassland conversion to cropland reduces habitat for native species and alters soil properties
• Overexploitation of resources, such as overfishing, poaching, and unsustainable harvesting, can lead to population declines and ecosystem imbalances
  • Overfishing of top predators (sharks and tuna) can cause trophic cascades, altering marine food webs
  • Poaching of elephants for ivory has led to population declines and disrupted seed dispersal in African savannas
• Invasive species, often introduced by human activities, can outcompete native species and disrupt ecosystem functioning
  • Kudzu, a fast-growing vine from Asia, smothers native vegetation in the southeastern United States
  • Burmese pythons, released as pets, prey on native mammals in the Florida Everglades
• Climate change is exacerbating existing threats to ecosystems, causing range shifts, phenological mismatches, and increased vulnerability to disturbances
  • Warming temperatures are causing coral bleaching and the loss of coral reef ecosystems
  • Changing precipitation patterns are altering fire regimes in grasslands and forests
• Conservation efforts aim to protect and restore ecosystems through various strategies:
  • Protected areas, such as national parks and wildlife reserves, safeguard habitats and species
  • Habitat restoration projects, like reforestation and wetland rehabilitation, help recover degraded ecosystems
  • Sustainable resource management practices, such as ecosystem-based fisheries management and sustainable forestry, balance human needs with ecological integrity
  • International agreements, like the Convention on Biological Diversity, promote global cooperation in conservation efforts

Case Studies and Examples

• Yellowstone National Park: Reintroduction of gray wolves in 1995 led to a trophic cascade, reducing elk populations and allowing the recovery of riparian vegetation, benefiting beavers and other species
• Great Barrier Reef: Rising ocean temperatures and acidification due to climate change are causing coral bleaching and the loss of coral reef ecosystems, impacting the diversity of marine life and local communities dependent on reef-based tourism and fisheries
• Amazon Rainforest: Deforestation for agriculture, logging, and mining is fragmenting habitats, causing biodiversity loss, and altering regional and global climate patterns through changes in carbon storage and water cycling
• Serengeti Ecosystem: The annual migration of wildebeest and zebra shapes the savanna landscape, maintaining grassland productivity and supporting a diverse array of predators and scavengers, such as lions, hyenas, and vultures
• Mojave Desert: Adaptations of plants and animals to extreme heat and aridity, such as the Joshua tree's deep roots and the desert bighorn sheep's ability to obtain water from succulent plants, demonstrate the resilience of life in harsh environments
• Himalayan Mountains: Altitudinal zonation of biomes, from subtropical forests at the base to alpine tundra at high elevations, showcases the influence of elevation on ecosystem distribution and the adaptations of species like the snow leopard and the Himalayan musk deer

Practical Applications and Research Methods

• Remote sensing techniques, such as satellite imagery and aerial photography, enable the mapping and monitoring of biome distribution, land-use changes, and vegetation dynamics
  • Landsat and MODIS satellite data are used to track deforestation rates, monitor wildfires, and assess the health of vegetation
• Geographic Information Systems (GIS) allow the integration and analysis of spatial data, such as topography, climate, and species distributions, to model ecosystem processes and predict future changes
  • GIS can be used to identify priority areas for conservation, plan habitat corridors, and assess the potential impacts of development projects
• Field surveys and long-term ecological monitoring provide ground-truth data on species populations, community composition, and ecosystem functions
  • The Long-Term Ecological Research (LTER) Network consists of 28 sites across the United States that have been studied for decades, providing valuable insights into ecosystem dynamics and responses to environmental change
• Experimental manipulations, such as controlled burns, herbivore exclusion, and nutrient additions, help elucidate the mechanisms underlying ecosystem processes and species interactions
  • The Nutrient Network (NutNet) is a global research collaborative that conducts standardized nutrient addition experiments in grasslands to understand the effects of fertilization on biodiversity and ecosystem functioning
• Ecological modeling uses mathematical and computational tools to simulate ecosystem dynamics, test hypotheses, and predict future scenarios
  • Process-based models, like the Dynamic Global Vegetation Model (DGVM), simulate the interactions between climate, soil, and vegetation to project changes in biome distribution and carbon cycling under different climate change scenarios
• Citizen science initiatives engage the public in data collection and analysis, expanding the scale and scope of ecological research
  • iNaturalist is a platform where users can upload photos of organisms and contribute to the mapping of species distributions, providing valuable data for biodiversity monitoring and conservation planning
• Interdisciplinary approaches, combining ecology with social sciences, economics, and policy, are crucial for addressing complex environmental challenges and developing sustainable management strategies
  • The Natural Capital Project brings together researchers, policymakers, and stakeholders to map and value ecosystem services, informing land-use decisions and investments in conservation and restoration