LandLand--based effects based effects –– a global issuea global issue

Estuarine and coastal ecosystems are Estuarine and coastal ecosystems are now under significant pressure globally now under significant pressure globally from human landfrom human land--based activitiesbased activities

Some of most serious problems Some of most serious problems (GESAMP 2001) include:(GESAMP 2001) include:

alteration and destruction of alteration and destruction of habitats and ecosystemshabitats and ecosystemseffects of sewage on human healtheffects of sewage on human healthwidespread and increased widespread and increased eutrophicationeutrophicationdecline of fish stocks and other decline of fish stocks and other renewable resourcesrenewable resources

change in sediment flow due to change in sediment flow due to hydrological changeshydrological changes

The past..The past..Once heavily covered in forest and scrubland, Once heavily covered in forest and scrubland, overlying in many cases highly erodible geologyoverlying in many cases highly erodible geology

History of active tectonics, strong storm and History of active tectonics, strong storm and rainfall dynamics rainfall dynamics –– the latter strongly mitigated by the latter strongly mitigated by vegetationvegetation

Following arrival of Maori, around half of Following arrival of Maori, around half of vegetation removed by burning, mainly around vegetation removed by burning, mainly around coastal plains, lakes and riverscoastal plains, lakes and rivers

Following arrival of Europeans, clearing moved Following arrival of Europeans, clearing moved into the back country, extensive areas converted to into the back country, extensive areas converted to pasturepasture

Reduced slope stability, substantially increased Reduced slope stability, substantially increased land slide rates, and erosionland slide rates, and erosion

Development of pastoral economyDevelopment of pastoral economy

Inputs of sediments to the coastal zone are now Inputs of sediments to the coastal zone are now especially high by world standards, approaching especially high by world standards, approaching almost 1% of total world sediment yieldsalmost 1% of total world sediment yields

Physical change – the evidence

Physical evidence Physical evidence –– sedimentationsedimentation

Sedimentation Accumulation Rates (SAR)Sedimentation Accumulation Rates (SAR)

E.g.E.g. WhangamataWhangamata estuary, Coromandel; c 700 B.P. estuary, Coromandel; c 700 B.P. SAR rates of c 0.01 mm yrSAR rates of c 0.01 mm yr--11,, 11 mm yr11 mm yr--11 afterafter18801880 c. 5 mm since 1940c. 5 mm since 1940’’ss

Marlborough Sounds Marlborough Sounds –– direct forestry inputs to direct forestry inputs to coastal system (Fahey & Coker 1992)coastal system (Fahey & Coker 1992)

Queen Charlotte Sound Queen Charlotte Sound –– background erosion background erosion 300300––600 t km600 t km--22 yryr--11. Forestry roads added 62 t, . Forestry roads added 62 t, increasing to 218 t at harvesting, with a further increasing to 218 t at harvesting, with a further 20% from log landings20% from log landings

Background sediment concentrations in seawater Background sediment concentrations in seawater c.c. 1515––20 mg l20 mg l--11, rising to 1000 mg l, rising to 1000 mg l--11 during storms during storms ((OO’’LoughlinLoughlin 1980)1980)

Physical evidence Physical evidence –– eutrophicationeutrophication

Effects on freshwater systems are well documented..Effects on freshwater systems are well documented..

Lowland rivers in agriculturally developed areas have been subjeLowland rivers in agriculturally developed areas have been subjected to high cted to high nutrients, turbidity and faecal contamination, leaving them in anutrients, turbidity and faecal contamination, leaving them in a poor conditionpoor condition

Streams in areas of dairy farming, especially where poor practisStreams in areas of dairy farming, especially where poor practises of shed effluent es of shed effluent disposal have been used, are in particularly poor condition, anddisposal have been used, are in particularly poor condition, and the intensification of the intensification of farming associated with dairying in general has also been relatefarming associated with dairying in general has also been related to increasing levels d to increasing levels of nutrients, sediments and faecal bacteria of nutrients, sediments and faecal bacteria

In pastureIn pasture--dominated catchments (>50% cover), most lakes have clarity leveldominated catchments (>50% cover), most lakes have clarity levels and s and nitrogen and phosphorus concentrations that breach water qualitynitrogen and phosphorus concentrations that breach water quality guidelinesguidelines

Physical evidence Physical evidence –– eutrophicationeutrophicationPoorly understood for coastal ecosystemsPoorly understood for coastal ecosystems

ARC monitoring ARC monitoring -- N and P are often N and P are often elevated due to adjacent landelevated due to adjacent land--basedbasedactivitiesactivities

Strong temporal correlations observed Strong temporal correlations observed between streams and estuaries between streams and estuaries streamstreamwater quality is a major determinant of water quality is a major determinant of water quality at adjacent inner harbour water quality at adjacent inner harbour sites.sites.

Savage (2009) Savage (2009) –– Southland nearSouthland near--shoreshoreenvironmentenvironment

Strong positive linear relationship Strong positive linear relationship between % of agricultural land in a between % of agricultural land in a catchment, and total nitrogen (N) loading catchment, and total nitrogen (N) loading to nearto near--shore environmentsshore environments

Secondary producers (fish; Secondary producers (fish; spottiesspottiesNotolabrusNotolabrus celidotuscelidotus, and estuarine , and estuarine triplefinstriplefinsGrahaminaGrahamina nigripennenigripenne)) growth generally growth generally enhanced in nutrientenhanced in nutrient--enriched coastal enriched coastal areasareas

Physical evidence Physical evidence –– eutrophicationeutrophication

ZeldisZeldis 2008a, b2008a, b

Two nutrient input sources possible: from the Two nutrient input sources possible: from the land via freshwater flows, or from the oceanland via freshwater flows, or from the ocean

Golden Bay Golden Bay –– c 12% from rivers, Tasman c 12% from rivers, Tasman Bay c 9%. Bay c 9%.

Firth of Thames Firth of Thames -- rivers contributed around rivers contributed around 70% of dissolved inorganic nitrogen (DIN) 70% of dissolved inorganic nitrogen (DIN) load, dropping to around 50% when load, dropping to around 50% when upwelling activeupwelling active

Likely that its productivity is substantially Likely that its productivity is substantially higher now than before the arrival of humanshigher now than before the arrival of humans

Suggested that pastoral catchment Suggested that pastoral catchment development has resulted in strong effects on development has resulted in strong effects on the Firth of Thames ecosystemthe Firth of Thames ecosystem Firth will Firth will respond to changes in catchment respond to changes in catchment management to the extent that it affects management to the extent that it affects nutrient loadingnutrient loading

Catchment – Driven System

Catchment DIN inputs - 70% of Firth total • Land use: Intensive farming, major inputs from dairy; • Firth has large terrestrial nutrient supply, esp. organic matter.

Freshwater and nutrients enter from Aorere, Takaka, Motueka, Wairoa Rivers and many smaller streams, groundwater and wastewater. - managers have an interest in gauging their influence.

Nutrients enter the bays through oceanic supply and freshwater inflows.

The bays receive waters from western Cook Strait, influenced by upwelling in the D’ Urville Current – these can have high nutrient levels.

~35 km

~40 km

Physical evidence Physical evidence -- pollutionpollution

Monitoring by regional councils and others Monitoring by regional councils and others heavy metal concentrations are often heavy metal concentrations are often strongly locally elevated around built up human settlementsstrongly locally elevated around built up human settlements

ARC report by Kelly (2007) for Auckland region: copper, lead, ziARC report by Kelly (2007) for Auckland region: copper, lead, zinc all increasing at nc all increasing at the most impacted sites the most impacted sites –– currently below threshold levels (TEL sediment quality currently below threshold levels (TEL sediment quality guideline values), but strong relationships with invertebrate coguideline values), but strong relationships with invertebrate community structure mmunity structure (intertidal flats)(intertidal flats)

Review of Auckland intertidal shellfish by Grant & Hay (2003): Review of Auckland intertidal shellfish by Grant & Hay (2003): ““While acknowledging that there are significant knowledge gaps, iWhile acknowledging that there are significant knowledge gaps, in general it appears that n general it appears that the occurrence of potential stressors at high levels are relativthe occurrence of potential stressors at high levels are relatively rare and localisedely rare and localised”” and thatand that““there is a general trend of increased risk of anthropogenic contthere is a general trend of increased risk of anthropogenic contaminants in interaminants in inter--tidal zones tidal zones in enclosed estuarine areas as opposed to open coastal environmein enclosed estuarine areas as opposed to open coastal environmentsnts””..

Physical evidence Physical evidence –– river plumesriver plumes

Large South Island east coast rivers Large South Island east coast rivers –– lowlowsalinity plumes extending at least 100 km salinity plumes extending at least 100 km along the coast during high flow eventsalong the coast during high flow events

North Island North Island –– Raglan,Raglan, AoteaAotea andand KawhiaKawhiaHarbour plumes extending to 20 km offshore Harbour plumes extending to 20 km offshore during storm events. during storm events.

MotuekaMotueka RiverRiver –– surface salinity plume can surface salinity plume can extend more than 20 km into Tasman Bayextend more than 20 km into Tasman Bay

Major flood event with the appropriate Major flood event with the appropriate wind directions can push north around wind directions can push north around Separation Point and into Golden BaySeparation Point and into Golden Bay

Area of c. 50 kmArea of c. 50 km22 around mouth around mouth naturally contaminated with heavy naturally contaminated with heavy metals. Benthic influence to at least 6 km metals. Benthic influence to at least 6 km out from river mouthout from river mouth

What coastal fisheries species are likely to be What coastal fisheries species are likely to be impacted?impacted?

Coastal FisheriesCoastal FisheriesExtensive range of species harvested, from Extensive range of species harvested, from the intertidal out to the continental shelfthe intertidal out to the continental shelf

Commercial catch (Ministry of Fisheries Commercial catch (Ministry of Fisheries 2008)2008)

Cockles 1,345 tCockles 1,345 tPipiPipi 135 t135 tScallops 713 tScallops 713 tPauaPaua 995 t995 tBluff oysters.. Bluff oysters..

Flatfish 4,050 tFlatfish 4,050 tSnapper 6,328 tSnapper 6,328 tTrevallyTrevally 2,987 t2,987 tLeatherjackets 454 tLeatherjackets 454 tRed gurnard 3,817 tRed gurnard 3,817 tJohn dory 815 tJohn dory 815 tTerakihiTerakihi 5,729 t5,729 tKahawaiKahawai 2,500 t2,500 tBlue cod 2,403 tBlue cod 2,403 t

BlueBlue mokimoki 504 t504 tRed cod 5,551 tRed cod 5,551 tElephant fish 1,148 tElephant fish 1,148 tSchool shark 3,719 tSchool shark 3,719 tRig 1,362 tRig 1,362 t

41,367 t finfish..41,367 t finfish..

Possible mechanisms of impactPossible mechanisms of impactIncreased sedimentationIncreased sedimentation

Direct effects on organisms e.g. clogging, Direct effects on organisms e.g. clogging, shading, visual effectsshading, visual effects

Indirect effects e.g. loss of shelter, food Indirect effects e.g. loss of shelter, food production, settlement surfaces, settlement production, settlement surfaces, settlement cuescues

EutrophicationEutrophicationIncreased nutrients Increased nutrients algal blooms; algal blooms; reduced water clarity, light levels, oxygen reduced water clarity, light levels, oxygen levels, changes in benthic assemblageslevels, changes in benthic assemblages

PollutionPollutionChemical compounds, heavy metalsChemical compounds, heavy metals

Changes in freshwater flow, river plumesChanges in freshwater flow, river plumesMultiple effects on the behaviour and Multiple effects on the behaviour and dynamics of estuarine and marine dynamics of estuarine and marine populationspopulations