Lecture 14: Application of Ecosystem Ecology to Management

Principles of Ecosystem-Based Management

• Underlying concept: Human activities influence ALL ecosystems 

  • Local land use change, global biogeochemical cycles, climate, biodiversity

    • Management needed to mitigate impact 

• Principles of management:

  • State factors: External factors that control the structure of an ecosystem and how it functions

  • Cannot be locally managed BUT interactive controls can be

  • Interactive controls: dynamic factors that directly influence and interact with one another to shape overall structure and function of the ecosystem. 

    • Soil resources, disturbance regime, functional groups of organisms and human activities 

  • 1. Conserve interactive controls:

    • Maintaining natural disturbance regime (“normal conditions” with disturbances) 

    • Natural rivers will have peak streamflow in the spring due to the snow melting + runoff 

      • Dams prevent flooding and transport of sediment, in order to restore to natural regime, tear dams down

    • Native trees rely on periodic flooding and sediment inputs to grow 

      • Invasive trees prevent the establishment of native trees; thus, they must be removed

  • 2. Stabilizing feedbacks (maintaining and enhancing):

    • Recall: positive feedback = amplifying and push system further from og state; negative feedback = restoring and bringing system back to og state 

    • Population control of herbivores by predators (ex. Yellowstone wolves = keystone species)

      • Trophic cascade initiated when wolves were reintroduced = stabilizing feedback to elk population because there was an abundance of elk due to no predators 

      • Since red deer are preventing the regeneration of native conifer, wolves should be introduced to bring the population down 

  • 3. Landscape perspective: how land and water interact 

    • Deforestation upstream will increase the streamflow which leads to an increase in sediment, lowering water quality 

      • In order to protect the fish sensitive to these changes, managing watersheds is needed

    • Mangroves = buffers for tropical coastal ecosystems from storms/erosion (many efforts to protect them)

    • Wetlands & barrier islands (formed when river sediment deposited near mouths of large rivers) 

      • Dams and levees hinder sediment development which has resulted in loss of wetland and barrier islands 

      • As a result, hurricanes have had larger effects on mainland; thus, they must be protected and restored 

  • 4. Resilience (maximize in order to be able to bounce back better) 

    • Helps to maintain diversity (species diversity is stable through redundancy, insurance hypothesis) 

      • Insurance hypothesis: when multiple species within an ecosystem perform similar functions (functional redundancy), it acts like an "insurance policy" against environmental disturbances, ensuring that if one species declines, others can take over and maintain ecosystem function, thus promoting stability and resilience. 

    • Resilience promoted by stabilizing feedbacks 

      • Macrophytes take up nutrient abundance (stabilizing) -> results in bloom that reduces oxygen and light -> zooplankton consume phytoplankton to reduce the effects (stabilizing) -> predators of zooplankton keep them in check 

  • 5. Adaptive potential (ability to adjust management plans to new conditions)

    • Major dams decide when/how much water to release to allow water provisioning with conservation goals 

• Management based on single species populations:

  • Population dynamics theory: Examines how the size and composition of a population changes over time, considering factors like birth rates, death rates, migration, and interactions with other species within their environment 

  • Fisheries management 

    • Goal: extracting maximum sustainable yield (MSY)

    • MSY = when population growth is the fastest but there are often crashed due to temporal variation and interactions in ecosystem components 

      • Collapse from technology allowing an efficient harvest = overfishing?

      • Population is struggling to rebound due to the competing dogfish dominating 

      • Misstep due to food web not being taken into account in the single species population models 

    • How to resolve the issue? Ecosystem based approach to management

      • Conservation of Antarctic Marine Living Sources to dictate how much krill can be harvested annually 

      • Utilized concepts of food web to determine value of sustainable harvesting 

      • Lowered by 25% to maintain critical food source for the whales

  • Forestry management: 

    • Traditionally focused on efficiency (maximal extraction rates after peak NPP) and areas are replanted with mono-specific trees that are susceptible to disease and are not suited for the wildlife present 

    • Ecosystem based management: interactive controls

      • Maintain the natural disturbance regime by selectively harvesting to promote regeneration 

        • Leaving patches of trees or treefalls 

      • Keep some biomass on the ground so SOM can replenish and there are nutrients 

      • Plant N-fixating plants to accelerate the newly planted trees 

• Management for sustainability: 

  • Takes into account multiple economic and conservation goals and addresses interactions between social and ecological processes 

    • Considers people components of regional systems 

    • Ex. Great Barrier Reef has certain areas where research and touring can happen; also has area where no one can go 

• Ecosystem services (Trade-offs & Synergies)

  • Ecosystem services: the benefits people get from ecosystems (can be defined by $)

    • Value of ecosystem services very high ($61 trillion dollars)

  • Advantages: allows comparison of different management options using $ 

    • Intact ecosystems worth more to society over extractive values of their goods 

    • NY city water: from Catskill mountain 

      • Development in the 90s impacted water quality and filtration plant would cost $$$

      • As a result, land was bought to halt the damage to the wetlands 

      • Bonus: became a tourist attraction

    • Coffee: top 5 most valuable crops from developing countries 

      • Employs 25 million people and is grown in high biodiversity 

      • Since coffee is so popular, major deforestation is occurring to harvest them = biodiversity loss

      • Animal pollinators rely on intact forests for habitat; bee pollination increases yield by 15-50%

      • Coffee farm makes $60k/year so intact forests patches must be protected so bees can continue to pollinate farms 

  • Disadvantages: ethical issues, determining which species/plants  are most important to society

    • Loss of vultures in India

      • Livestock were treated with medicine which made vultures sick and die = decline in population (lost 3 species)

      • No vultures = increase in scavengers such as feral dogs 

      • Feral dogs = more rabies = death of many people = money lost ($24 billion)

    • More animals = lower disease spread

      • Mice are the best host and disturbed areas support them

      • Squirrels/lizards are bad and dilute the virus; found in intact forests (ideally we want more of these) 

      • Ground predators reduce mice population 

    • Lyme disease is costly to treat and so there is a lot of value in protecting biodiversity for dilution effects 

  • Trade-offs and synergies: 

    • Managers focus on one or a few services

    • Sustainability requires multiple services thus trade offs are needed 

      • Trade off: one desirable feature comes at the expense of another

        • Ex. natural forests replaced by agriculture industry 

        • Scarce economic resources, no point in conserving them because too costly 

      • Synergy: multiple desirable outcomes are accomplished through one action 

        • Ex. Dams can generate hydroelectric power and brings in money from tourism 

          • But dams promote loss of habitat and downstream floods/sediment transfer

        • Ex. Preserving intact forests prevents carbon emissions = protecting earth 

• Restoration (feedbacks): intentional activity that initiates or accelerates the recovery of an ecosystem with respect to its health, integrity, and sustainability 

  • Response to disturbance dependent on four factors:

    • 1. Resistance: tendency to not change

    • 2. Response: magnitude of change

    • 3. Resilience: rate of return to original state

    • 4. Recovery: extent of return to original state 

  • Stabilizing feedbacks needed to push system back

    • Ex. seeding native species, re-introducing mycorrhizae (to add organic matter into soil), and restoring grazing/disturbance regime 

  • How to create stabilizing feedbacks in invaded landscape 

    • Fast growing invasive species = short life span = no defensive exterior = preferred by herbivores 

    • Conservation grazing: selectively choosing when to allow animals to graze invaded lands 

      • Native grazers no longer present in many areas 

  • N deposition can cause amplifying feedbacks but has been helping invaded landscapes as alternative stable state

    • More N = invasive species grow faster 

    • Decompose quickly and accelerate N mineralization to amplify feedback and favor more invasion 

      • How to fix? Add carbon to create stabilizing feedback

        • Adding c causes bursts of microbial activity 

        • High C:N ratio - microbes will immobilize soil nutrients, lowering N in plants 

        • Since there is less nitrogen, fast growing plants no longer dominate and slow growing native species will 

        • Adding carbon favors the native over invasive species = stabilizing feedback 

    • Exotic annual grasses will grow earlier (early phenology) which allows them to take resources first = exotic dominance 

      • Priority advantage = flexible germination cues but mistiming disadvantage 

    • Watering pulses at a random time will deplete exotic seedbank 

    • Allows for restoration by pushing the invasive species away