loss of biodiversity

what is causing biodiversity variation and change?

  • natural processes 

    • disturbance

    • competition

    • predation

  • these usually maintain the biodiversity

  • human caused drivers:

    • land cover change

    • chemical release/pollution

    • overfishing/overharvesting

    • climate change

    • etc. (other human impacts)

global cumulative human impact (CHI)

  • 87-90% of the ocean surface has been impacted by humans

  • Halpern et al. 2019 data show that some areas have

    • hgh CHI + fast increasing change

    • high CHI + decreasing change

    • low CHI + decreasing change

  • human impacts are global, and the pace of change differs among regions

marine defaunation

  • marine defaunation started tens of thousands of years later than on land

  • defaunation is less severe in the ocean than on land

  • humans have impacted 87-90% of ocean surface

  • marine fish abundance has decreassed by 38% since 1970

  • marine habitats such as seagrass and mangroves have decline by > 2/3

land-cover change

  • human casued land cover change typically decreases species richness

  • but by creating a more heterogenous habitat, richness can increase

  • during recovery after disturbance, richness can peak at intermediate stages, then decline at the climax stage

  • direction of impact depends on disturbance stage and habitat structure

chemical release/pollution

  • harmful pollutants (mine tailings, insecticides, acid rain) usually decrease richness

  • fertilizer effects are more complex

    • richness can increase or decrease

    • biomass of producers and detritivores usually increases

overharvesting

  • nonselective harvesting → drastically decreases biomass and species richness

  • selective harvesting (e.g. targeting top predators) can cause predator release → sometimes increasing biomass or richness

  • impact direction varies

climate change

  • climate change alters physical and chemical properties of oceans.

  • species responses vary within and between groups

  • ocean warming leads to:

    • increases in warm water species

    • poleward shifts

    • depth shifts

    • responses where geographical barriers block movement

  • other impacts listed:

    • changes in reproduction, growth, survival

    • changed in ocean currents affecting dispersal

  • calanus ratio in the north sea has increased, illustrating warm-water dominance with warming

ocean acidification

  • OA leads to declines in calcification in corals and coccolithophores

  • it affects growth, reproduction, and organisms with calcium carbonate shells/skeletons

  • some positive effects exist, e.g., algae (enhanced photosynthesis or fewer predators)

  • many species are experimentally sensitive to OA

  • little filed evidence so far; warming dominates current patterns

  • some field studies (calcifying plankton, foraminifera) show patterns consistent with OA

  • undersaturation is occuring faster than expected in the western arctic

  • projections suggest more impacts in the future

the source of extinction threats

  • its mentioned from the given papers which we will come to soon

global policy frameworks

  • a new global framework (CBD draft 2030)

  • target includes:

    • 30% protection of land and sea

    • 50% reduction in invasive species introduction

    • reduce nutrients by half, pesticides by two thirds

    • eliminate platic waste discharge

  • UN SDGs relevant

    • goal 13: climate action

    • goal 14: life below water

    • goal 15: life on land

debate on biodiversity change

  • globally: extinctions increasing

  • locally: many argue species richness is not declining

  • biodiversity trends are complex and vary with scale

  • important to ask: what is diversity

types of biodiversity

  • species diversity → many species with similar abundances

  • genetic diversity → how closely related individuals are; needed for adaptation

  • ecosystem diversity → number of ecosystems in a region

  • functional diversity → range of behaviours / ecological function of species

biodiveristy metrics: ⍺- and β diversity

  • ⍺-diversity

    • number of species at a site

    • species richness

    • most commonly measured

  • β-diveristy

    • change in species composition over space/time

    • turnover

biodiversity trends at different scales

  • global scale:

    • speciation ≠ extinction balance → extinctions increasing

    • ⍺-diversity decreasing

  • biogeographical scale

    • alpha-B (biogeographic scale alpha diversity) increasing

  • regional (meta-community) scale

    • trends hypothesized, not well measured

  • local scale

    • no significant trend in alpha diversity across studies

    • large variation among sites

trends in spatial β-diversity

  • β-diveristy tends to decrease → sites become more similar over time

  • this is homogenization

  • leads toward a more spatially homogenous planet

winners (generalists) vs losers (specialists)

  • generalists adapt better to changes → tey increase

  • specialists decline → they lose

  • this lead to functional homogenisation

conclusions from the lecture

  • biodiveristy trends depend on scale

  • multiple metrics must be used

  • be critical - biodiversity numbers can be misinterpreted

  • trend: moving towards a more homogenous planet

why biodiversity matter?

  • ecosystem functioning depends on:

    • species richness

    • species composition

    • functional group richness

    • genetic diversity

  • ecosystem stability depends strongly on species richness/composition

  • therefore:

    • biodiversity declines → less stable ecosystems

global extinction rates

  • 90% of marine organisms extinct over earth history

  • background rate = 0.01-2 extinctions per million species per yeat

  • current = 100x higher

  • humans dominate biogeochemical cyces and biodiversity patterns

  • ocean acidification has been associated with three of five past mass extinctions

  • first time such changes are human driven

state of the ocean (Luypaert et al. summary slide)

  • humans impacted 87-90% of oceans

  • marine fish abundance down 38% since 1970

  • coastal habitats (seagrass, mangroves) depleted by two thirds

  • CO2 up 40% vs pre industrialisation

  • degraded ecosystems → lost ecosystem services

  • increased reliance on ocean as land degrades → more pressure

extinction of marine species (Webb & Mindel summary slide)

  • marine extinctions appear lower than terrestrial 

  • but nuber of marine species is uncertain (estiamtes range: 300,000 - 2.2 million)

  • only 240,000 marine species described → 11-78% known

  • extinction risk assesment depends on taxonomic knowledge

  • IUCN focuses on well-known groups

  • apparent low marine extinction rate due to lack of knowledge, not low risk

why non-scientific communities doubt biodiversity decline?

  • public thinks changes are natural fluctuations

  • people lack trust in data

  • need clear communication and evidence to build trust

shifting baseline syndrome

  • concept: each geenration acceps a degraded state as normal

  • introduced by pauly (1995)

  • leads to underestimating long-term losses

  • examples shown from Oslo fjord:

    • histroical sprat fisheries

    • many whales in the fjord in 1890

    • old fishing maps showing abundant fishing spots

lecture summary:

  • multiple human dirvers interact to change biodiveristy

  • impacts can increase or decrease richness depending on mechanism

  • global patterns show strong defaunation but complex local trends

  • need to measure alpah and beta diveristy across scales

  • the planet is becoming more homogenous

  • generalists rise, specialists decline

  • biodiveristy underpins ecosystem functino and stability

  • marine extinction appears low but is actuaally underestimated

  • shifitng baselines distort human perception of loss

the papers - Luypaer et al. 2020, Webb and Mindel 2015, Herbert-Read et al. 2022

integrated explanation

  • together these papers provide a full picture of where marine biodiveristy stands today, how threatenened it actually is, and what fufutre pressures are coming

the state of marine biodiversity today

  • human impact is nearly universal

    • 87-90% of the global ocean surface is impacted by human activities

    • these include exploitation, habitat degredation, climate change, and pollution

  • major delcines already documented

    • marine fish abundance has declined by 38% compared to 1970

    • coastal habitats such as seagrass meadows and mangroves have been depleted by more than two-thirds

    • atmspheric CO2 has increased by 40%. relative to pre industrial levels, accelrating ocean acidification

  • possible mass extinction trajectory

    • over 90% of marine organisms that have ever lived are extinct (natural background extinction)

    • but current extinction rates are 10x the bacjground rate, suggesting we may be entering a human-driven mass extinction

  • ocean services are weakening

    • as ecosystems degrade, the oceans’s ability to deliver ecosystem services decline

    • if land based ecosystems degrade further, pressure on marine resources will increase even more

  • marine biodiversity is declining significantly, but the full extnet is hard to measure due to knowledge gaps

why marine extinction appear lower than on land

  • marine species appear to have lower extinction and extinction-risk levels - but this is misleading

  • apparent extinction rates

    • only 19-24 marine species out of > 850 documented global extinctions → this looks like a low marine extinction rate

    • but the paper shows that this result is biased by limited knowledge

  • most marine species are not described

    • estimated number of marine species ranges from 300,000 to 2.2 million

    • only about 240,000 have been formally described → this means 11-78% of marine species remain unknown

    • since extinction risk can only be assessed for described species: we underestimate marine extinction risk simply because we lack data

  • low assessment effort

    • only 3% of described marine species have been assessed by the IUCN

    • many marine taxa have no assessments at all

  • when we do have data, risk is similar to land

    • when the paper compares well-studied groups (both marine and terrestrial: 20-25% fo species are threateneed with extinction in both realms

    • in other words: the true marine extinction risk is simialr to terrestrial levels but hidden due to low taxonomic and conservation assessment efforts

  • data-deficient species

    • 28.6% of marine IUCN assessments are data deficient

    • DD species often have traits associated with high extinction risk

  • the ocean doesnt have fewer threateneed species - we just know far less about them. The low risk narrative is an illusion created by lack of data

emerging issues that will impact biodiversity in the next 5-10 years

the horizon scan identifies 15 emerging issues likely to storngly affect marine biodiverisry soon. These issues fall into three categories

  • ecosystem impacts:

    • wildfire impacts on coastal/marine ecosystems

      • fires release nutrients, metals and particles that wash into the ocean

      • can cause eutrophication, mortality of benthic invertebrates, or temporary productivity increases

    • coastal darkening:

      • increased turbidity and dissolved organic matter reduce light penetration

      • affects photosynthesis, species composition, and coastal habitat function

    • increased metal toxicity due to ocean acidification

      • lower pH increases bioavailability and toxicity of chemicals

      • affects marine organisms and potnetially human health (via seafood)

    • declining equatorial biodiversity

      • equatorial regions are losing species as thermal zones shift poleward

      • creates a dip in diversity around the equator

    • lower nutritional content of fish due to climate driven changes

      • changes in phytoplankton fatty acids affect foodwebs and human nutrition 

  • resource exploitation:

    • marine collagens

      • increasing demand for collagen may drive harvesting og sponges, jellyfish, sharks, etc.

      • risk of increased pressure on non-target species

    • expanding trade in fish swim bladders

      • extremely lucrative trade drives overexploitation

      • bycatch threatens species such as sharks, rays, turtles

    • fishing of mesopelagic species

      • huge biomas but critical for the biological carbon pump

      • large scale harvesting could disrupt carbon sequestration

    • deep sea lithium extraction

      • higher lithium demand (e.g. batteries) may shift mining to deep sea brines

      • deep brine ecosystems contain many endemic and largely undescribed species

  • new technologies

    • colocation of marine activities

      • combined uses (wind farms + aquaculture) require new regulatory frameworks

    • floating marine cities

      • could alter species movement, increase invaive species, and raise governance issues

    • trace element contamination form green technologies

      • battery waste and production release nickel, cobalt, and other toxic elements

    • new underwater tracking systems

      • could improve study of non surfacing animals, but ecological impacts are unknown

    • soft robotics

      • useful for deep sea sampling but may introduce pollutants or disturb organisms

    • biodegradable materials

      • green plastics may still causes harm; theri long term impact is unknown

    • new threats are emerging rapidly, mnay of which are poorly understood or not yet included in management plans

take home message

  • marine biodiversity is already declining severly, is more threateneed than it appears due to huge knowledge gaps, and will face additional emerging threats in the coming years

  • together the three papers present a consistent picture:

    • the ocean is heavily impacted by real extinction risk is underestimated

    • new, poorly understood pressures are emerging rapidly

  • this reinforces teh lectures themes:

    • biodiversity is declining globally

    • trends differ across spatial scales

    • generalists may increase, specialists decline

    • management decisions depend on good data - but marine biodiversity is understudied

    • future pressures may increase homogenization and degredation