L17- Rebuilding Ocean Life

Where are we now?→ the pressures on marine ecosystems:

• there are many pressures on marine ecosystems:

  • exploitation

  • habitat loss

  • pollution

  • climate change

1. exploitation

• total global catch in fisheries→ bars go above reported, includes estimated unreported and illegal fishing too, 100mt by 1990s and has remained relatively constant since

  

  → we take a huge biomass out of fisheries every year

• hunting of marine megafauna→ daily locations of american whaling vessels show a huge density of points when whales were sited or caught from, does not include data from other countries too

  

  • huge loss of whales, estimated using models:

2. habitat loss

• there is lots globally and lots around coastlines

3. plastic waste pollution

• increased massively and is continuing to increase

4. climate change

• ocean continues to warm, heat waves are driving coral bleaching, increase in sea surface temp and heat content of upper 2000m, increases year on year

when did the pressures start/where are they going?

• there are lots of human pressures that started a long time ago, lots have peaked (hunting, fishing, deforestation, habitat loss) but some are recovering whilst some are growing

  

What can we do?→ 4 categories of impactful interventions for marine ecosystems:

• regulate hunting

• manage fisheries

• improve water quality

• protect and restore habitats

1. regulate hunting- issue/scale:

• whaling has occurred for centuries but the late 19th century had technological advances and processing capabilities that led to huge losses by the 20th century

• scale of this→ 3million whales were killed and processed in this time, all major whales were hit:

  

1. regulate hunting→ solution/now:

• since then, the International Whaling Commission decided commercial whaling needed to stop for 1985-1986, some countries did not listen, is still in place→ has ended commercial whaling:

  • fin whales population was reduced to 1-2% of its pre-exploitation size but recent surveys have reported huge returns to ancestral breeding grounds→ are a recovering population

1. regulate hunting→ conclusion:

• global agreements to reduce/halt exploitation leads to recovery of hunted populations

2. manage fisheries→ issue/scale:

• fish in NE Atlantic have been intensely commercially exploited for decades, primary driver of decline is fisheries

• fishing biomass and mortality:

  • above 1→ biomass is healthy and at maximum sustainable yield

  • below 1→ fishing mortality is within maximum sustainable yield

  • fishing biomass decreased (reached maximum) and fish mortality increased (went above maximum) since 1970

  • there was wide spread exploitation

  • management pattern has reversed these effects

  

2. manage fisheries→ assessments:

• global coverage of the RAM database (the largest database of fisheries stock assessments)-

  • proportion that have a scientific assessment, size of pie chart is how much is caught

  • there are many stocks that are well assessed, but there are certain areas where the stocks are barely assessed

  

• have been well monitored→ can understand the pressures on them:

  • below→ things we can’t control, influenced by environment, predation etc.

  • above→ things we can control, fisheries, can influence that through fisheries management

  

2. manage fisheries→ management:

• better management from 2000 had led to an increase in fish biomass

• large scales fisheries can be managed sustainably- have the understandings

• lots of fish stocks that have been exploited since 2006 now have fishing pressures below the maximum sustainable yield but lots of other stocks have increased in fishing pressures

  → reducing fishing pressure promotes fish stock rebuilding

• full recovery will take years

• how actively and effectively managed fish stocks are→ increases in intensity of management will cause a decrease in fish mortality and an increase in biomass

  

2. managing fisheries→ conclusion:

• fish stocks with robust scientific assessments are well managed and increasing in fish

• reducing fishing pressure promotes fish stock rebuilding

3. improve water quality→ management

• there are many regulations/frameworks being developed to reduce sewage in oceans

  • Stockholm convention, MARPOL convention→ have reduced pollutants in the sea

3. improve water quality→ e.g.

• e.g. the baltic sea→ ‘time machine’, is already affected by future impacts expected to be seen in other seas

  • is enclosed, need international agreements:

  

• heat map of stresses in seas→ the baltic sea has the highest, with high to intermediate in all these stressors

3. improve water quality e.g. management:

• there has been an effort to improve water quality in this sea e.g. nutrient pollution (agricultural and industrial runoff)

• successful management has lead to a regional trend reversal in nutrient pollution→ both types of nutrient are above target loads but trends are downwards

  

3. improve water quality→ conclusion:

• can get substantial improvements in water quality by implementing easy solutions but full recovery is more costly and can cause conflict with other areas

4. protect and restore habitats→ solutions:

• MPAs- has increased to over 8% today

  • well protected MPAs do work→ increase fish biomass by 3x, fish density increases by 40%, spillover benefits, habitat benefits

• initiatives to restore habitats

  • direct restoration measures- number of measures have increased over time and in multiple habitats e.g. project seagrass

  

4. protect and restore habitats→ conclusion:

• coastal and marine habitats can be protected and restored but the issue is how to scale them up

Roadblocks to recovery of marine life:

• natural variability

• environmental extremes

• natural/social events

• increased pressures from the human population

• failure to mitigate climate change

• gaps/biases in understanding

managing data-limited fisheries issues:

• only 50% of stocks are scientifically assessed

• there are no scientific assessments on small scale fisheries in coral reef and mangrove habitats

• these stocks need qualitatively different types of assessments e.g. species specific vs mixed-species

climate change issues and solutions:

• are not on target to meet targets e.g. Paris Agreement

• spatial and habitat based conservation can help e.g. habitat restoration and MPAs can improve carbon sequestration, protection, biodiversity, catch and incomes

MPAs study→ ability to mitigate climate change:

• meta analysis from 200 MPAs show how marine habitats can help mitigate climate change:

  • how much they contribute to different pathways, global extent of habitat (size of circle)

  • have different effects

  • sediments don’t have much effect, just a little carbon sequestration, but cover most of the planet so globally this will have an impact

→ MPAs alone cannot offset all carbon but are a useful tool for climate change mitigation

Beyond managing crises:

• Duarte et al. suggest a 2050 target of substantial to complete recovery for most oceans is realistic

• futures:

  • managing high seas as global commons

  • science fiction prototyping→ imagining what oceans will look life, stepping back and looking at what future we want, optimism