geo-engineering challenges to marine biodiversity

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Geo-Engineering Challenges to Marine Biodiversity

Richard Norris; SIO-UCSD

Major challenges to Marine BiodiversityDirect human impacts (immediate effects)

• Reduce biodiveristy & resilience• Both top-down and bottom-up impacts• Reduce mobility in face of climate change

Human environments typically: • species poor • short food-chains

homogeneous • disturbed • have imported energy and

nutrients

Major challenges to Marine Biodiversity

Indirect human impacts (long-range impacts) due to Global change

• Acidification• Stratification• Altered PPT patterns• Storm and sea-level impacts on coasts

Keeping Perspective

Consider the nature of impacts that would exist under a business-as-usual scenario

Partial solutions may be preferable to no solution

…But there are worries that partial solutions will sap political will to act

Three types of Geo-engineering Albedo enhancementReflectors, Cloud production and Ground-based albedo enhancement

Land-based Carbon SequestrationCO2 into oil wells, saline aquifers, Enhanced weathering

Ocean-based Carbon SequestrationOcean dumping of CO2, Biochar, Nutrient fertilization, Enhanced weathering

Can also think about just two categoriesMethods that change the chemistry of systems• These typically address the acidification issue

as well as climate change

Those that do not…. • Usually only deal with temperature

Albedo-enhancing Geo-engineering ConsequencesCommon themes—no reduction of:

• CO2 absorption in ocean• acidification

• environmental loading of other waste products of fossil fuel burning—NOx, SOx, trace metals (many of them heavy metals)• NOx already a problem in coastal water ways

• Carbon-particulates (ash)

Reflectors in spaceChanges albedo at the top of the atmosphere• Because these are in space, the main impacts on

ecosystems come from potential changes in weather systems, ppt, land-sea contrasts, and continued acidification

• Diminished UV may also affect composition of surface ocean phytoplankton

Reflectors in spaceImpacts from changes in weather

• Severity related to shifting ‘natural’ processes into new frequency, geographic position, or stable states.

• Mucking around with the PDO, NAO and other multi-decadal cycles

• e.g. Mantua et al. 1997, Bull Am, Met. Soc• Of course, all these happen anyway with global change.

Cloud Seeding with Salt Spray Increasing cloudiness:• Changes community structure toward low-light intensity communities

with potential impacts on export production;

Clouds may affect air-sea temperature contrast• Storm intensity & evaporation weakened (Mahmud 2009 Singapore J

Trop. Geography) • Implications for nutrient exchange between thermocline and surface. • Create a permanent, local el-Niño?

Shepard et al. 2009after Latham et al, 2008

Some other impacts of cloud ‘whitening’Water removal could affect:• Larval abundance and viability (like desalination plants)

Permanent installations • Act as giant open-ocean habitats (Fish Aggregation Devices) for

highly-migratory fishes and marine mammals

SO2 addition to atmosphereAcid rain• Sure, but the ocean is big and relatively well mixed• More of a problem for poorly buffered terrestrial systems• BUT, deposition on snow or ice could create a runoff acid pulse

to coastal waters—problematic for Arctic, Antarctic…

www.swisseduc.ch/glaciers

SO2 addition to atmosphereOzone destruction • increases UV influence in surface ocean

• but ocean absorbs UV efficiently• Experiments show some diatoms (Pseudo-nitzschia) do well in high UV waters (Mengelt & Prezelin (2005) Mar-Ecol. Prog Series)

• UV also reduced overall phytoplankton production (Llabres & Agusti 2010 Aquatic Microb. Bio; Finkel et al. 2010; J. Plank. Res)

• Could be a problem for seabirds, seal colonies (walrus, fir seals, elephant seals…)

Ground-based albedo enhancementThese seem unlikely to have a major impact on marine communities • Unless they alter weather

• Water runoff

• Sediment and nutrient transport by wind, streams or dissolved ground water flows.

Ocean-based C-Sequestration Major impacts from land-based enhanced weathering:• Could change the flows of dissolved compounds (like

bicarbonate ion) and cations into ocean water.

• Waste streams are likely to be concentrated • Have many of the same impacts as saline outfall from desalination

plants

• Could offset ocean acidification • But this depends upon where outfall is delivered

• Local alkalinity spikes might contribute to ‘whitings’

Trace metals are the problem• Peridotite is not a completely benign substance

• due to imbalances in Mg/Ca ratios• High concentrations of Ni, Co, Cr; low Mo • A “serpentine barrens” of the sea?

US Forest Service

Enhanced WeatheringDumping effluent from enhanced weathering like other waste streams• Tend to produce reduced biodiversity & short food

chains

Ocean-based Carbon Sequestration Consumption of other bio-limiting nutrients• Causes Fe-fertilization to ‘rob’ downstream

communities of nutrients

Shortening food chains• Changes in marine community structure depending

upon type of phytoplankton production

• increased primary production would likely shorten food chains and reduce biodiversity.

Nutrient FertilizationO2 consumption• Impacts of doubling c-flux to the sea floor on

benthic communities • Ocean O2 (Keeling et al. 2010, Ann Rev Mar. Sci; Shaffer et al. 2009

Nature Geosci)• Models already predict up to ~60% volume of ocean

affected by ocean hypoxia in coming millennia• A return to the Cretaceous?

Ocean-based Carbon Sequestration Biochar storage in the ocean• Potential habitat for wood-loving taxa;

• if stored as wood or biomass has short lifecycle owing to ship worms (>> Century)

askNature.org

Geo-engineering-final thoughts• CO2 removal either by political will or technology

deals with most problems• CO2 dumping in ocean could be problematic if

not neutralized by carbonate or buried.

• From a biodiversity perspective, solutions that leave acidification in place are the most dangerous (e.g. albedo enhancement)

• But, in short-term, direct human impacts are the major threat