BIEB 176 Midterm 3

SRM reduces earth surface temp but

When you stop SRM, temp rapidly increases

How to create stabilizing feedback, lowering soil N availability?

C additions cause burt in microbial activity High C:N ratio substrate causes microbes to immobilize soil nutrients Lower soil inorganic N availability to plants Puts fast growing exotic species at a disadvantage Favors slower growing native species

Potential light scenerios

1: Low light and deep mixed layers, high nutrients, low herbivory 2: Light increases with season and stratification, nutrients available, low herbivory 3: High light nutrients depleted, high herbivory Blooms dominated by large phytoplankton such as diatoms which in turn have large predators such as copepods and krill These larger phytoplankton and zooplankton tend to export carbon and nutrients from the surface Strong biological pump

Disturbance

A relatively discrete event that removes organic material, such as plant biomass and/or soil Often terrestrial An event that alters the structure of populations, communities and ecosystems and causes changes in resource availability or the physical environment (marine/freshwater)

Maximize resilience

Ability to rebound following disturbance Maintaining diversity Species diversity confers stability through redundancy, insurance hypothesis

Regime Shift

Abrupt changes in community structure and function, encompassing multiple variables, and often including key structural species Regime shift often used to describe big changes that are not necessarily from one stable state to another

Carbon nutrient retention

Accumulation of soil carbon and rising CEC over time As colonizers allow C in SOM to accumulate, soils develop CEC that allows retention of cation nutrients

Valuation of ecosystem services

Advantages Allows comparison of different management options using a common currency Often is is surprising how much intact ecosystems are worth to society, over and above the extractive values of their goods Pollinators can pollinate coffee more if there are more intact forests Disadvantages Ethical issues Existence values of a species What happens when a species is too costly? Which species or places are most important? Lyme disease Squirrels will dilute the spread Rats will spread it to humans

Microbial loop

After bloom nutrients tend to be recycled locally within the surface ocean

Effects of light

All else being equal, photosynthesis rate increases with light At high levels of light, rates of photosynthesis can saturate and even decline Photoinhibition

Effects of Nutrients

All else being equal, phytoplankton grow faster when nutrients are plentiful At high nutrient levels, growth saturates Due to there being a limit on how much can be taken in Nutrients includes macronutrients such as nitrate, phosphate, and silicate but also micronutrients such as iron

Pros and cons of Forest protection as a flexibility mechanism to help achieve goal of bending the curve

Benefits Protects biodiversity Often cheaper to protect forests than other investments such as large scale energy efficiency tech Concerns Disturbances like fire and storms can make the permanence of forest carbon uncertain There are trade offs with other uses, for instance forest protection could result in loss of logging jobs

Carbon capture

Captured CO2 stored in rocks or deep ocean Effectiveness High Feasible, with no inherent limit on size of effect achievable CDR method so addresses cause of climate change and ocean acidification Very large potential but requires additional carbon storage Affordability Low Potential high costs of CCS at source Timeliness Low Slow to reduce global temp Much more R and D required to find cost effective methods Would require substantial infrastructure construction Safety Very high Minimal undesirable side effects Limestone heated using renewable energy Released CO2 stored, here in concrete

Changes in Precipitation

Changes to precipitation get more dramatic when you look into the future If you're somewhere where it is already wet, it is likely to get wetter If you're somewhere where it is already dry, it is likely to get drier Extreme rainfall events and floods are more likely in warmer climate

Ecosystem based approach to managing sustainable fisheries

Commission for the conservation of antarctic marine living resources decides how much krill can be harvested each year in international waters around antarctica Management for sustainability Not management for a single product or species Maintain multiple economic and conservation goals Addresses interactions between social and ecological processes Considers people components of regional systems Traditional forestry focused on efficiency Max extraction rates, clear cut, after the stand reaches peak NPP Areas replanted with mono-specific stands, vulnerable to pests, disease Doesn't support the full suite of wildlife present before harvest

Limitations of species distribution model (SDMs)

Competition might limit establishment Assume individuals can disperse Lots of barriers to dispersal Velocity of climate change is faster for flat areas than steep elevation gradients, many species may not be able to disperse fast enough to keep pace Species may not establish if they have other habitat requirements

Why do small phytoplankton dominate when nutrients are scarce?

Diffusive supply of nutrients proportional to cell radius Diffusive supply a = 4pirD D is diffusion constant, r is cell radius Nutrient demand is proportional to cell vol Constraints that cells be small to acquire resources eases Small phytoplankton tend to have small zooplankton grazers that rapidly consume new growth Larger phytoplankton tend to have larger grazers that are, on average, more slowly growing This decoupling between phytoplankton growth and zooplankton grazing allows large cells to survive when nutrients are abundant

Ecosystem based forestry management

Douglas fir is an important lumber species in the pacific NW extensive forests need to be managed for sustainability Financial Ecological habitat Northern spotted owl Managing the interactive controls Disturbances Tree Falls/patch fires natural disturbance regime Selective harvesting rather than clearcutting maintains patches for wildlife, promotes regen Soil resources Removing all biomass prevents nutrients and SOM replenishment Leave slash on the ground Functional types Plant N-fixing alders in the understory to accelerate the growth of newly planted trees

Tradeoffs between establishment and longevity through succession

Early colonizers produce many seeds, short lifespan Later colonizers don't produce as many seeds, but live a long time, competitively dominant later Early colonizing, fast growing plant species tend to be more palatable to herbivores Higher quality Mammalian herbivores speed succession by removing early successional species Moose remove fast growing willows Speed nutrient cycling

Space based methods

Effectiveness High No inherent limit on effect to global temps SRM method does nothing to counter ocean acidification Affordability Low to very low High cost of initial deployment but long lifetime once deployed Timeliness Very low Would take several decades at least to put reflectors into space Once in space, reflectors would reduce global temps within a few years Safety Medium Residual regional climate effects, particularly on hydrological cycle No known direct biochemical effects on environment beyond possible effects of reduced insolation

Interannual Variations due to ENSO

El Nino Warm episodes La Nina Cold episodes El Nino periods in tropical and eastern pacific tend to be warmer than normal La Nina periods in tropical and eastern pacific tend to be cooler than normal Chlorophyll reduced in el nino periods in tropical pacific and California Current because stratification stronger, upwelling reduced, and nutrient delivery weaker ENSO index describes temp anomalies in tropical Pacific (warm = El Nino, Cold = El Nina)

Bottom up effects of ENSO

El Nino years have higher rainfall, immediate increase in vegetation This leads to increase in herbivores one year later and predators a year after that Changes in environment and marine phytoplankton associated with ENSO felt in higher trophic levels Bottom up forcing

Conserve interactive controls

Ex. maintain natural disturbance regime Natural rivers have peak streamflow in spring with snowmelt and runoff Dams prevent flooding and sediment transport downstream Invasive Tamarisk is a tree invading many riparian areas in W US Prevents native tree establishment Solution: Restore the disturbance regime

Export Production Change

Export production is the flux of particles out of euphotic zone Export production decreases globally but may increase in some high latitudes where phytoplankton growth is light and/ or temp limited Affects biological pump Increasing stratification decreases flux of carbon out of atm Leaves more CO2 in atm Destabilizing effect on climate Weakens biological pump

Human Health

Extreme heat waves are likely to become more frequent in a warmer climate Infrastructure Changes in sea level can impact infrastructure Developing coastal and island nations face major impacts from rising sea levels

What factors explain the characteristics of changes in plant communities over the course of succession

Facilitation Especially early in succession Introducing organic matter for soil formation, N-fixation Life history trade offs Fast colonizing (many small seeds), short lived species replaced by slow colonizing, long lived species Herbivory Can speed succession by preferentially removing fast growing species, allowing slow growing species to establish

How to create stabilizing feedback in an invaded landscape?

Fast growing invasive species may be less defended and hence preferred by herbivores Many native grazers are no longer present in many areas Conservation grazing companies have been established to graze invaded lands at optimal times during the season to favor natives

Initial colonizers differ in primary vs secondary succession

First colonizers in successional environments are important, dispersal depends on seed size Small seeds can disperse long distances Large seeds can only disperse short distances Primary succession colonizers have small seeds Late successional species have large seeds and are slow growing Secondary succession colonizers have a range of seed sizes and fast growth rates

Management approaches based on single species populations

Fisheries and forestry management Goal Extract max sustainable yield (MSY) from the system Based on population dynamics theory (MSY) when pop growth is fastest Problem Population crashes due to temporal variation and interactions among ecosystem components

Adaptive capacity

Flexibility to adjust management plan based on experiments/new info Many examples with water provisioning Each year major dams in W US decide how much water to release downstream and when Allows them to balance their needs with the ecosystem's

Patterns of NPP reflect succession

Forest productivity often peaks in mid succession NPP initially rapidly increases, due to species replacements, N inputs NPP declines following canopy closure Species replacements, slower growing spp later in succession Decreased nutrient availability as stands age More bound in SOM, humus The total pool of biomass will continue to slowly increase even as C flux in through NPP decreases Check graph

What drives species replacements and ecosystem change over time?

Glacier bay alaska, rapid glacial retreat in 200 years Observe patterns of species abundances and soil properties, where the ecosystem has had different amounts of time to develop Species replacements driven by facilitation Facilitation Where the presence of one species benefits another Moss and lichen add organic matter to create basic soil Drayas and Alder litter acidifies soil, favors spruce establishment Slow decomp, organic carbon increases water holding capacity of soils, hemlocks establish

Compared to early climate models, modern climate models:

Have higher spatial resolution Represent more physical, chemical and environment processes Include biology and ecology on land/water Leverage considerable intellectual and computational advances Have been vetted for decades

Is herbivory considered a disturbance?

Herbivores consume biomass in all ecosystems Not considered disturbance if not causing directional change in species composition/ecosystem function Insect epidemics can cause large scale plant mortality Forests with many dead trees are more likely to burn

Managing feedbacks in restoration

If restoring an invaded or disturbed landscape, may need stabilizing feedbacks to push system back towards original state Seeding native species Reintroduce mycorrhizae Restoring the grazing/disturbance regime If a system is stuck in an alternate stable state, may require novel techniques to remove any amplifying feedbacks preventing recovery

Resilience is also promoted by stabilizing feedbacks

In clear lakes macrophytes take up nutrient pulses Stabilizing High eutrophication can cause phytoplankton bloom, reduce light and O2 Zooplankton can consume phytoplankton, reduce harmful bloom Stabilizing Fish predators reducing zooplankton can dampen this resilience mechanism

How do changes in pCO2 impact phytoplankton?

Increasing pCO2 impedes the growth of some phytoplankton but enhances the growth for others

Solar radiation management (SRM)

Influence climate by reducing the amount of sunlight absorbed by earth Also called solar geoengineering or albedo modification

Ecological restoration

Intentional activity that initiates or accelerates the recovery of an ecosystem with respect to its health, integrity and sustainability (SER)

Amplifying feedbacks caused by N deposition may be maintaining invaded landscape as an alternate stables state

Invasive species increase in abundance with N deposition More than slower growing natives Decompose quickly accelerate N mineralization, amplifying feedback favoring further invasion

Changes in water balance following disturbance

Less transpiration when veg is removed by disturbance More runoff Leftovers after plant water uptake Runoff decreases with time after disturbances

Human activities influence all ecosystems

Local land use change Global biogeochemical cycles, climate, biodiversity Hence all ecosystems require some level of management Decisions to do nothing will cause ecosystems to change We have an ethical responsibility to manage/mitigate anthropogenic impacts

Sustaining multiple services

Managers often focus on one or a few services Fish pops, timber, freshwater Single service focus usually fails to max public benefits Sustainability requires sustaining multiple services Trade offs or synergies among services Trade off = one desirable feature comes at the expense of another Synergy = when multiple desirable outcomes are accomplished through one action

Nitrogen cycling changes through primary succession

Moose speed N cycling Early to middle Fixation by alders High N inputs Middle Increasing dominance by conifers Low N availability Early Slow decomp and mosses bind N Late

How do organisms respond to climate change?

Move in space Move in time Change behavior Acclimate Change physiology but not DNA Evolve Change underlying DNA and physiology More likely for shorter lived organisms Change in fitness and abundance In extreme cases, extirpation or extinction

Temporal Succession

Much of the temp, high latitude, and upwelling ocean exhibits strongly seasonal environmental conditions As a result, seasonal cycles in plankton biomass and community structure as ubiquitous Seasonal succession of species linked to their particular traits and interactions with predators Species composition influences ecosystem function

Carbon fluxes also vary with time since disturbance

NPP max in mid-succession Heterotrophic respiration (decomposition) Lags C input NEP is the balance between NPP and decomposition NEP = 0 at steady state Carbon fluxes vary between types of succession NEP can be negative in secondary succession, due to decomposition of remaining organic matter following disturbance Otherwise following a similar pattern to primary succession Check graph

Stratification Changes on Organisms

Nutrient limited area You will exacerbate the limited nutrients Less nutrients available Light limited area Increase in stratification can increase production Will spend more time at surface instead of being mixed into water column

Nutrient cycling in secondary succession

Nutrient retention is greater during secondary than primary succession because of SOM in soil Pulse of nutrient availability after disturbance Fate of nutrients depends on retention mechanisms Plant uptake Low early in succession Microbial uptake Chemical fixation Cation exchange sites If not taken up, nutrients are likely to be lost through leaching

Carbon export pulses following blooms

Nutrient stripped out of surface and exported downwar, replenished in the following winter when mixed layer deepens again

Phenological mismatch may disrupt mutualisms

Phenology of the ground nesting silver bee is more sensitive to increasing temps and less sensitive to solid moisture, than the beach pea that it pollinates Land managers can use phenological monitoring to identify species at risk from climate change

Methods

Place reflective objects in space Inject stratospheric aerosols Brighten marine clouds Make ocean more reflective Increase albedo on man made structures Grow more reflective plants

2 types of succession

Primary Start from parent material (no soil) Severe disturbances remove most living organisms Colonization is far from seed source E.g. glaciers, volcanic eruptions. Shifting floodplains Secondary Disturbance less severe, start with soil Plants can resprout or regenerate from seed bank Fire, hurricanes, pest outbreaks

Ocean fertilization

Primary productivity and drawdown of carbon is limited by nutrients in much of the ocean Adding nutrients particularly to subtropical regions, would increase phytoplankton growth and sequester CO2 How effective is it? In best case, only a small fraction of new primary production would be exported to deep ocean Only if carbon is exported to deep ocean will it remain there for more than 10's - 100's of years At most, carbon sequestered for 1000's of years Sinking organic matter consumed O2 and can produce OMZ Lowers pH in deep water Fertilizing ocean surface changes marine ecosystem structure Replacing/favoring certain types of organisms Effectiveness Low Likely to be feasibly but not very effective CDR method so addresses cause of climate change And would reduce ocean acidification in the surface waters but not deep ocean May reduce biological carbon uptake elsewhere in ocean Likely low long term carbon storage potential Affordability Med Not expected to be very cost effective Especially for methods other than iron fertilization Timeliness Low/Very low Slow to reduce global temps Substantial prior research required to investigate environmental impacts, efficacy and verifiability

Valuing forest carbon

Protection of intact tropical forests prevents carbon emissions from deforestation Global carbon market values avoided emissions Additional co benefits/synergies Biodiversity protection, maintenance of surface properties, maintain natural capital for local communities

What can be done to reduce changes in the climate and their impacts?

Reduce greenhouse gas emissions Geoengineering Deliberate large scale intervention in earth's climate system in order to moderate impacts of anthropogenic greenhouse gas emission

Agricultural activities that can decrease C storage in soils

Reduced tillage or no tillage Reduces soil disturbance Use of cover crops, especially N fixing crops to reduce fertilizer use Planting crops with high root allocation, especially perennial species Organic matter amendments, adding carbon directly to soil

Water provisioning

Reductions in snowpack Lower recharge to reservoirs Impacts on wildlife Warming results in earlier spring streamflow and drier summers San diego faces increasing water demand and falling supply

Carbon dioxide removal (CDR)

Remove excess CO2 from the atm and store the carbon in the land biosphere, ocean or deep geological reservoirs

Ecosystem response to disturbance depends on

Resistance Tendency not to change Response Magnitude of change Resilience Rate of return to original state Recovery Extent of return to original state

Seasonal dynamics in terrestrial ecosystem C fluxes

Respiration peaks after GPP Soil takes longer to warm than air in the spring Microbes require labile C inputs to become active NEP can be pos in spring or neg in autumn NEP = Net ecosystem production Pos NEP means C is accumulating Climate drives global scale variation in species compositions among biomes But local variation in species composition and ecosystem processes is often driven by variation in disturbance history and subsequent recovery

An argument against geoengineering

SRM does not remedy impacts of increasing CO2 CDR reduced CO2 but it is still not clear how scalable CDR could be SRM and CDR would have to be continued indefinitely or climate could precipitously warm SRM would likely have negative impacts on plant growth, could deplete ozone and lead to acid deposition Both SRM and CDR would lead to unknown changed in regional climate SRM is likely to impact hydrological cycle Ocean fertilization is likely to have negative impacts To date, there is tremendous uncertainty about how geoengineering would impact the entire, coupled climate system This is particularly true for SRM Geoengineering may lessen incentives to reduce emissions Moral hazard Human error Huge and enduring costs Procedural justice" → Who decides how much to change climate? What happens when a country (perhaps unilaterally) modifies the climate of another country? "Distributive justice" → Benefits and harms of geoengineering will be spread unevenly among people Will geoengineering be conducted by governments or private entities? Will profit be involved?

Sources of uncertainty for climate models

Scale/resolution Imperfect understanding of natural processes Natural climate variability Unknown future emissions

Species can respond to climate change by altering their phenology

Seasonal timing of developmental events Leafing, flowering, hatchings Determines the environmental conditions and biotic interactions experienced by individuals Highly sensitive to environmental cues Varies among species Shifting phenology observed worldwide provides evidence that climate change is already impacting species and ecosystems Earlier spring events Species that "track" climate by having earlier phenology with warming have higher performance than species which don't shift their phenology

Properties of disturbance regime

Severity Amount of organic matter removed Intensity Energy released per unit area/time How hot was the fire? How strong were the winds? Frequency Often? Rare? Type Fire, glacier, storm, disease outbreak Size/pattern Small patches or the whole landscape? Timing Soon after disturbance or after many years of undisturbed conditions

Marine cloud brightening

Ship tracks over North Pacific Instead of DMS, use sea salt Would require a global fleet of 1000's of ships operated continuously Effectiveness Low to med Feasibility Limited max effect and limited regional distribution Affordability Med Very uncertain, short aerosol lifetime at low altitude so requires continual replenishment of CCN material but at lower cost per unit mass Timeliness Med Once deployed would start to reduce temp within one year Could be deployed within years/decades Safety Non-uniformity of effects May affect weather patterns and ocean currents Possible pollution by CCN material

Interactive controls can be managed

Soil resources Disturbance regime Functional groups of organisms Human activities (some)

Principles of management

State factors constrain ecosystem structure and function but most can't be locally managed Interactive controls can be managed Conserve interactive controls Maintain and enhance stabilizing feedbacks Landscape perspective Maximize resilience Adaptive capacity

Positive NAO Phase

Stronger pressure gradient, stronger winds, wind positions shifted further to north Stronger winds in spring weakened spring phytoplankton bloom (lower light on avg), warmer temps negatively affect C. finmarchicus

Changes in energy balance

Successional changes in boreal forest after fire Albedo decreases immediately after boreal forest fire More energy absorbed by dark surface Afterwards increases mid succession Why the increase? Herbaceous and deciduous vegetation in mid-succession has higher albedo than the pre-fire conifer forest

Land use changes

Terrestrial ecosystems absorb ~30% of CO2 emissions Currently 20% of greenhouse gas emissions come from land use change, primarily deforestation Reducing deforestation, afforestation (new forest) and reforestation would reduce CO2 in atm Effectiveness Limited potential for carbon removal Low Affordability Very high Cheap to deploy Timeliness Med Ready for immediate deployment and starts CO2 reductions immediately Slow to reduce global temps (CDR method) Safety High Few undesirable side effects except for potential land use conflicts and biodiversity implications

Ecosystem services

The benefits people obtain from ecosystems Many can be defined by economic value

Mixed Layer Depth

The depth over which the physical characteristics (temp, salinity, density) in the upper ocean are nearly uniform Same as surface Stratification = density difference between the surface and depth Usually density at 200 meters With deep mixed layer, more nutrients are entrained into surface mixed layer Phytoplankton growth increases with increased nutrients As surface cools in winter, mixed layer deepens and entrains more nutrients to the surface Depletion of nutrients in summer due to consumption by phytoplankton and shallower mixed layers that limit vertical supply

Why trust physical climate projections?

There is considerable confidence that climate models provide credible quantitative estimates of future climate change, particularly at continental scales and above this confidence comes from The foundation of the models lie in accepted physical principles From their ability to reproduce observed features of current climate and past climate changes Model can predict observed climate that we've seen already Can attribute which process has caused it

Amount of light available for photosynthesis decays exponentially with depth

Time averaged light experienced by phytoplankton in the case of deeper mixed layer would likely be lower than case of shallow mixed layer Shoaling of mixed layer can increase the amount of light experienced by phytoplankton, increase rates of photosynthesis Provided photoinhibition does not occur In light limited regions of the ocean (high latitudes mainly), phytoplankton blooms can occur when mixed layer is shallower Conversely, blooms can be inhibited when mixed layer is deep In nutrient limited regions of the ocean (low latitudes mainly), blooms are more tired to nutrient supply Deepening the mixed layer increases phytoplankton production in these area

Evolution in the face of global change?

Traditional larval food plant was Plantago lanceolata Larval food plants and nectar plants have declined throughout the range, competition with invasive plants Observed a shift to a new host plant

International climate policy

UN treaties are negotiated by consensus while slow it is an equitable way to reach agreement IPCC is a scientific body acting to inform the UNFCCC negotiations, rigorously peer reviewed and free from politics, represents best scientific evidence on climate change Many ethical issues: developed countries accounted for the majority of past emissions, what role should developing countries play?

Species replacements over time are driven by

Variation in traits of the dominant species Small seeds early. Bigger seeded and slow growing species later Species interactions Facilitation enhances (early) Competition slows (late)

Surface Temp Changes affect Stratification

Warms the water on the surface making it less dense and increases stratification Warming and salinity change generally lead to increased stratification and reduced supply of nutrients to surface Reduce flow of nutrients to surface Lowers primary productivity Lowers oxygen in large areas of ocean Increased stratification leads to reduced ventilation of ocean interior Change in Ocean pH Changes in sea level Different ranges of sea level rise

Argument for Geoengineering

We have failed to meaningfully reduce emissions of greenhouse gasses Climate change is having and will continue to have significant impacts on humans and ecosystems While wealthy nations and communities may be able to adapt to climate change, the impacts may be severe in developing countries and lower income communities Technology is emerging both SRM and CDR to reduce climate change impacts Some types of CDR face little opposition and have low potential risks If successful, geoengineering could lessen human suffering and damage to ecosystem Scientists should engage in geoengineering research to increase efficacy and decrease uncertainties Geoengineering should be conducted according to so-called Oxford principles Geoengineering regulated as public good Public participation in geoengineering decision making Disclosure of geoengineering research and open publication of results Independent assessment of impacts Governance before deployment

Negative NAO phase

Weaker pressure gradient, weaker winds, wind position shifted further to south Weaker winds in spring strengthened spring phytoplankton bloom (higher light on avg), cooler temps favor C. finmarchicus

Terrestrial Range Shifts

With increasing temps, we expect species to shift their distribution across the landscape to track their climate envelope Towards the poles, up in elevation Average increase in elevational ranges of small mammals Individual species responses were mixed, with both range expansion and contractions

Increase in temperature consequences

Yellow fever mosquito Range expansion with warming In recent years new Aedes mosquito species have been observed in San Diego county Sea level is rising Projected sea level rise will result in losses of beach and wetland areas, impact property Longer droughts in S. California and more wildfires expected

What is a climate model?

You take the earth, ocean and atm and cut it into cubes Then will use those cubes to do math on them Resolve processes within each grid cell Integrate models forward in time