Transcript Overview of Human Impacts - University of California, Davis

Announcement
***Seminar Today***
• “Lethal Sound: Submarines, Sonar and the
Death of Whales”
• Joel Reynolds, Senior Attorney, Natural
Resources Defense Council
• Tuesday Oct. 2 (TODAY) 5:00-7:00 pm
• Buehler Alumni Center
Overview of Human Impacts
Fishing and Overexploitation
• Fish and shellfish are taken for a range of uses
including food, raw materials, medicines, pets
and collections
• Fishing effort continues to increase with bigger
and faster boats and better equipment
• Large percentages of many stocks are taken
– In eastern U.S., > 90% of the eastern rock lobster is
harvested annually
– In North Sea, 60-70% of the haddock is harvested
annually
• 75% of the world’s fisheries are fully or
overexploited and 33% of the U.S. stocks are
overfished or depleted
World’s Fisheries Catch
Fishing and Overexploitation
• Target species are managed in isolation typically
with no management of resources they need
• Although impacts on populations often decline
with abundance, fishing for particularly valuable
fishes (swordfish grouper, tuna) may not
• Overfishing may result in serious declines and
even endangerment of coastal benthic species
(rockfishes) and species with vulnerable life
histories (groupers)
By-catch or Incidental Take
• Many species are captured unintentionally with
the target species
• These include many other taxa
– Other fishes
– Benthic invertebrates
– Marine birds, turtles, and mammals
• The most serious problems with by-catch are
associated with methods like gill netting and
bottom trawling
• Other methods such as long-lining are also
associated with loses as well
Gill Netting
• Gill nets are enormous nets that are left
adrift to capture fish
• Capture large numbers of open ocean
fishes nonselectively
• Also drown birds, mammals and turtles
• Frequently lost, these nets can “ghost fish”
for years
Bottom Trawling
• Trawling is among the most non-selectively
fishing methods
• Trawling involves dragging nets along the
bottom and captures fish nonselectively
• Finfish equal to 5-20% of the worlds entire
seafood catch is caught in shrimp trawls
• Before 1981, U.S. by catch in shrimp trawls
include 10 billion fishes and up to 55,000 sea
turtles annually
Bottom Trawling
• Trawling also creates several types of
disturbance
• Digging up deep sediments can result in
death due to siltation of sponges and
sensitive filter feeders
• Siltation can also affect light penetration
and hence deeper water algal
communities
Overexploitation
• Collection of species including fishes and
invertebrates for aquarium trade
• Intense collections of particular species often by
hand
• Unlike commercial fishing, when hand collected
species become rare, value increases
supporting continued exploit
• Economic projections indicate this will be an
increasing trend in developing island countries in
Asia
Coral Fishing
• Even smaller artisanal fishers often use
techniques with large effects
• Dynamite fishing in coral reefs has damaged
large areas of reef in the Indo-Pacific (e.g.
Philippines, Indonesia)
• Sodium cyanide, bleach, and rotenone are also
commonly used
• These kill corals reducing the local diversity of
the whole system
More Than Just Fish
• Not just fishes but whales, seals, birds and
turtles either are or have been heavily
exploited
• Several groups have been exploited for
food, oil, shells, feathers and other
products
• Some of these (Caribbean monk seal,
Japanese Sea Lion, Great Auk, Labrador
Duck) have been driven to extinction
Marine Mammals
• Baleen whales and large toothed whales have
been hunted for oil and meat
• Even smaller toothed whales including river
dolphins and belugas have been hunted to very
low levels
• Many Dall’s porpoise, bottlenose dolphins, pilot
whales are taken as well
• In some cases, dolphins are killed and used as
bait for other fisheries (crab, shark)
Sea Birds
• Sea birds have also suffered as well
• Flightless birds like penguins are
particularly vulnerable
• Ground and burrow nesters like
shearwaters, penguins, etc. are also very
vulnerable
• Hunting for feathers and eggs has driven
many species to near extinction
Turtles
• Six of the seven sea turtle species are
threatened or endangered
• As a source of food, oil (leatherbacks) and
aphrodisiacs (eggs)
• Shells and skins are also popular for
collectors
• Beach nesting makes these species
particularly vulnerable
Extinct Marine Species
From Carlton et al. 2003. Annual Review of Ecology and Systematics
Habitat Alteration
• A wide range of human alterations to coastal
landscapes regularly occurs
• Dredging and channeling
• Beach nourishment and grooming
• Construction of jetties, levies and breakwaters
• Anchoring and trampling
• Logging and mining
• Coastal development
Habitat Alteration
• Creation of shoreline structures has many
unintended consequences
• Structure like jetties, levies, rip rap,
breakwaters, seawalls destroy habitat
• Structures like jetties create down shore
erosion
• Structures like seawalls can prevent
migration of marshes and sea grasses as
sea level rises
Habitat Alteration
• Beach nourishment involves impacts to both the
source and deposit areas
• Mining sand resuspends sediments, changes
current and erosion patterns and can remobilize
pollutants
• Adding sand can also resuspend sediments and
add to siltation loads
• Beach grooming (seaweed removal) can impact
shore species and remove nutrients for high
beach habitats
Habitat Alteration
• Anchoring and trampling of areas is
common in tourist areas
• Anchoring by recreational fishing and
diving boats can significantly impact areas
of slow growing coral reefs
• Trampling of marshes, beaches and
intertidal cobble habitats can result in
“loving to death” favorite areas
Habitat Alteration
• Dredging and channeling can have significant
short and long term impacts
• Channeling can lead to erosion and subsidence
in estuaries and other soft sediment habitats
• Dredging resuspends fine silts that clog and kill
sensitive filter feeders
• Dredging and channeling may mobilize
pollutants
• Sediments and changing flow may produce
areas that can become hypoxic (low O2) or
anoxic (no O2)
Habitat Alteration
• Extractive activities like logging and mining have
multiple impacts
• Logging mangrove forests is happening
worldwide
• In addition to the outright loss of habitats, loss of
mangroves can exacerbate coastal erosion
• Mining and drilling can also cause sediment
resuspension, loss of habitat and chemical
pollution from drilling wastes (contaminants)
Habitat Alteration
• Coastal development can also have multiple
impacts in coastal and neashore areas
• Development and land use changes can
increase siltation and sediment transport
• Especially important in low silt habitats like coral
reefs
• Freshwater inputs are also important
– Loss of freshwater (San Francisco Bay)
– Too much freshwater from increased runoff
Biological Invasions
• Human activity has increase the rate of
introduction of non-native species
• It a natural process (like extinction) that we have
greatly increased (x 106)
• Biological invasions have a range of impacts
from immeasurable to devastating
• Introductions in the ocean are largely irreversible
• Impacts are difficult to predict in advance
Biological Invasions
• Introduced species can impact human recreation
– Algal blooms can make beaches unusable
– They can clog nets used by sport and commercial
fishers
• Introduced species can influence ocean water
quality
– Blooms of introduced phytoplankton can create red or
brown tides
• Can cover or damage aids to navigation, water
intakes, docks/piers/pilings
– Sessile invertebrates can rapidly cover hard surfaces
Biological Invasions
• Invasions can result in loss ecosystem function
and ecological extinction
• Habitats can changed entirely:
– Introduced plants can occupy open space or change
the primary producer base (Caulerpa seaweed,
Spartina alterniflora cordgrass)
– Introduced filter feeders (Asian mussel, like zebra
mussel) can remove plankton needed for others in
food chain
– Introduced predators may drive species to near
extinction
– Introduced diseases can devastate native populations
Biological Invasions
• Coastal areas, particularly estuaries are
among the most heavily affected
• Even relative pristine areas like coral reefs
have invasive species problems
• In San Francisco Bay, >90% of benthic
biomass is introduced
• A new species arrives every 12 weeks
• Creates loss of beta diversity, functional
extinction and potential for outright
extinctions
Spartina Invasion in
San Francisco Bay
Diseases
• Diseases are important and episodic
• Many diseases occur naturally, but their
frequency and extent can be altered by human
activities
• Other human mediated stressors (temperature,
contaminants, etc.) can create epidemics
• Human activities can also result in new diseases
like Toxoplasma pathogen (transmitted to
pinnipeds from cat litter disposal)
• Some pathogens have been implicated in coral
diseases and even bleaching
Diseases
• Disease epidemics may also occur as the result
of selective over fishing
• Oysters in Chesapeake Bay crashed due to
diseases beginning in the 1960’s (the diseases
may also be introduced)
• Selective fishing likely removed the largest/most
vigorous oysters leaving the smallest/less
vigorous
• Generations of selection may leave population
vulnerable
Diseases
• Climate change can interact with disease
– Band diseases (white band, yellow band, black band)
of corals is closely correlated with temperature
• Siltation and contaminants are also exacerbate
disease
– Increased tumors in fishes and shellfish in urban
harbors
• Land use change and desertification may also
affect disease
– Increased dust from Africa transported by winds to the
Caribbean exacerbate coral disease
Contaminants
• A wide range of contaminants affect marine
habitats almost everywhere
• These include not just petroleum, but radio
nucleotides, organics, metals, pesticides,
herbicides and solid waste
• Most systems are impacted by more than one
compound
• Effects of multiple contaminants are very difficult
to assess
Contaminants
• Oil drilling and transport results in oil
contamination on small and large scales
• Damage due to poisoning, coating, asphyxiation
– Seabirds, otters, pinnipeds at special risk
• Light fractions can be very toxic
– Affect invertebrates, floating eggs at surface
• Also toxic drilling muds
– Regularly released from offshore gas and oil
Contaminants
• Coastal industries and agriculture are big
contributors to this problem
• Non-point source pollutants include
pesticides/herbicides as well as nutrients
from farms and ag fields
• Some chemical contaminants are the
result of older point sources (factories)
Contaminants
• PCBs, PAHs, and others are often the
result of older point sources associated
with factories
• Many older point sources have come into
compliance with current laws
• Many organic compounds are long lived or
have accumulated in another form and can
be remobilized over time
Contaminants
• Nutrients like nitrates and phosphates in
large quantities are also pollutants
• Enter waters from non-point sources like
farms, vineyards, lawns, sewage effluent,
atmospheric deposition
• Eutrophication is an enormous problem in
many coastal areas
– Baltic Sea, Adriatic Sea, Arabian Gulf, New
York Bight
Contaminants
• Solid waste or trash occurs throughout the
world’s oceans
• Plastic debris kills unknown numbers of birds,
turtles, marine mammals
• Ghost fishing from abandoned traps also has
significant impacts in sensitive areas (e.g.
Northwestern Hawaiian Islands)
• Up to 7% of the stock in the lobster fishery
• Lost gill nets also have similar effects
Climate Change
• Human activities are also resulting in
changes to the atmosphere and climate
• These changes include:
– Increase in UV-B
– Increase (and decrease) in surface
temperature
– Changes in circulation
– Altered storm and rainfall patterns
– Rising sea levels
Climate Change
• UV-B radiation due to loss of stratospheric
ozone
• CFCs (chlorofluorocarbons) and related
compounds migrate to stratosphere and
degrade ozone for many years
• Can cause population reductions in some phytoand zooplankton and increase mortality in larval
fishes
• Effects on plankton in particular could influence
entire food web
Climate Change
• CO2 , methane and other green house
gases by most estimates are increasing
global temperature
• Warming of sea surface temperatures will
have many impacts
• Affect winds, surface and deep ocean
currents, habitats and organisms
Climate Change
• Temperature most important in shallow areas
and in poles (predicted to warm more)
• Corals and zooxanthellae symbionts are close to
their thermal limit
• Coral bleaching is highly correlated with
increased ocean temperatures
• May also result is shrinking of sea ice systems
and movement of sea-ice borders
Climate Change
• Changing temperatures can influence wind
patterns and thus ocean circulation
• Could negatively influence upwelling areas
such as along the California coast
• May change deep ocean currents
produced by sinking of saline polar waters
• Changes in ocean circulation may alter
equilibration of global temperature
Climate Change
• Increased melting of glaciers and polar ice
packs is resulting in rising sea levels
• In addition to threatening coastal cities it may
negatively effect marshes, sea grasses,
mangroves and other low elevation habitats
• Changes in coastal land use may not allow
habitats to migrate and will result in loss of
habitat
• Rising sea levels may drown slow growing
corals that cannot grow fast enough to keep up
Climate Change
• Global change can interact with other
stressors
• Impacts and occurrence of invasions,
disease, and contaminants can all be
multiplied by increased temperature,
siltation, nutrients, etc.
• Changes are moderate now, but
possibility of state change with rapid
temperature increase in the future
(more later on isotope stage 11)