Seagrass communities of the Great Barrier Reef and their desired state: applications for spatial planning and management

The research program reported here evolved from an interest in developing ecologically relevant target criteria that, if met, correspond to desired ecological outcomes (e.g. desired state) for the Great Barrier Reef World Heritage Area (GBRWHA) and to achieving the overarching objective of the Great Barrier Reef Marine Park Authority’s Long-term Sustainability Plan. The objective of the original National Environment Science Program (NESP) Tropical Water Quality Hub (TWQ) Project 3.2.1 Deriving ecologically relevant load targets to meet desired ecosystem condition for the Great Barrier Reef: a case study for seagrass meadows in the Burdekin region was to examine relationships between catchment inputs of sediment and seagrass desired state, and to compare these against the 2018 Water Quality Improvement Plan’s ecological targets. This objective was met using a case study in Cleveland Bay based on sediment loads from the Burdekin River and other smaller catchments that discharge into the bay (Collier et al., 2020). The techniques developed in the Cleveland Bay case study are used in the present report at the scale of the whole GBRWHA for NESP TWQ Hub Project 5.4. To achieve this we followed three steps: (1) a consolidation and verification of seagrass data at the GBRWHA scale, (2) an analysis of the distribution of GBRWHA seagrass habitat and communities, and (3) an estimation of a desired state target for communities with sufficient data. To achieve step 1, we compiled and standardised 35 years of seagrass survey data in a spatial database, including 81,387 georeferenced data points. Twelve seagrass species were recorded, the deepest of which (Halophila spinulosa) was found at 76 m. This database is a valuable resource that provides coastal managers, researchers and the global marine community with a long-term spatial resource describing seagrass populations from the mid1980s against which to benchmark change. For step 2, we identified 88,331 km2 of potential seagrass habitat within the GBRWHA; 1,111 km2 in estuaries, 16,276 km2 in coastal areas, and 70,934 km2 in reef areas. Thirty-six seagrass community types were defined by species assemblages. The environmental conditions that structure the location and extent of these communities included depth, tidal exposure, latitude, current speed, benthic light, proportion of mud, water type, water temperature, salinity, and wind speed. Environmental parameters interact with the topography of the reef and changes in the coastal plain, its watersheds, and its development with latitude. We describe seagrass distributions and communities that are shaped by multiple combinations of these environmental complexities and how that may influence marine spatial planning and environmental protection initiatives (Chapter 3). For step 3, we used more than 20 years of historical data (1995-2018) on seagrass biomass for the diverse seagrass communities of the GBRWHA to develop desired state benchmarks. Of the 36 seagrass communities, desired state was identified for 25 of them, with the remainder having insufficient data. Desired state varied by more than one order of magnitude between community types, and was influenced by the mix of species in the communities and the range of environmental conditions that define community boundaries. We identified a historical, decadal-scale cycle of decline and recovery. Recovery to desired state has occurred for coastal intertidal communities following the most recent declines in 2008 - 2012. A number of the estuarine and coastal subtidal communities have not recovered to desired state biomass in recent years (Chapter 4). This body of work provides a huge step forward in our understanding of the complexities of GBRWHA seagrass communities. We discuss the relevance of these research outputs to future marine spatial planning and management. This includes zoning in “representative areas”, hierarchical monitoring design (e.g. RIMReP), and the setting of ecologically relevant sediment load targets for desired state (e.g. Lambert et al., 2019). The updated seagrass data, seagrass distribution, community classification and desired state targets provides important new information for incorporation into marine spatial planning and management that is discussed in Chapter 5. These applications include: • Future assessments of non-reef habitats within the GBRWHA and GBRMP. • Assessing how risk and spatial protection intersect with seagrass communities and the role they play in protecting seagrass, e.g. Queensland State and Commonwealth marine parks, Fish Habitat Areas, Dugong Protected Areas, Port Exclusion Zones. • Expanding our spatial analysis to areas ecologically connected but outside of the GBRWHA such as Torres Strait, the Gulf of Carpentaria, and Fraser Island coast, where we already have seagrass data. • Designing a hierarchical seagrass monitoring design with coarse scales (intertidal, subtidal, estuary, coast, reef) and fine scales (36 communities). We have identified significant knowledge gaps that should guide future monitoring efforts (e.g. RIMReP and Queensland Land and Sea Ranger Program), including a lack of consistent and recent data for reef seagrass communities. • We identified communities where data is deficient, such as in estuaries where important seagrass communities have potential exposure to multiple threats for which more consistent environmental data would be valuable. • Identifying potential restoration sites. Our work has highlighted the critical role of historical data in understanding spatial complexity and for making informed management decisions on the current state of seagrass in the GBRWHA. Our approach can be adapted for monitoring, management and assessment of pressures at other relevant scales and jurisdictions. Our results guide conservation planning through prioritisation of at-risk communities that are continuing to fail to attain desired state

Investigation of Coastal Vegetation Dynamics and Persistence in Response to Hydrologic and Climatic Events Using Remote Sensing

Coastal Wetlands (CW) provide numerous imperative functions and provide an economic base for human societies. Therefore, it is imperative to track and quantify both short and long-term changes in these systems. In this dissertation, CW dynamics related to hydro-meteorological signals were investigated using a series of LANDSAT-derived normalized difference vegetation index (NDVI) data and hydro-meteorological time-series data in Apalachicola Bay, Florida, from 1984 to 2015. NDVI in forested wetlands exhibited more persistence compared to that for scrub and emergent wetlands. NDVI fluctuations generally lagged temperature by approximately three months, and water level by approximately two months. This analysis provided insight into long-term CW dynamics in the Northern Gulf of Mexico. Long-term studies like this are dependent on optical remote sensing data such as Landsat which is frequently partially obscured due to clouds and this can that makes the time-series sparse and unusable during meteorologically active seasons. Therefore, a multi-sensor, virtual constellation method is proposed and demonstrated to recover the information lost due to cloud cover. This method, named Tri-Sensor Fusion (TSF), produces a simulated constellation for NDVI by integrating data from three compatible satellite sensors. The visible and near-infrared (VNIR) bands of Landsat-8 (L8), Sentinel-2, and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) were utilized to map NDVI and to compensate each satellite sensor\u27s shortcomings in visible coverage area. The quantitative comparison results showed a Root Mean Squared Error (RMSE) and Coefficient of Determination (R2) of 0.0020 sr-1 and 0.88, respectively between true observed and fused L8 NDVI. Statistical test results and qualitative performance evaluation suggest that TSF was able to synthesize the missing pixels accurately in terms of the absolute magnitude of NDVI. The fusion improved the spatial coverage of CWs reasonably well and ultimately increases the continuity of NDVI data for long term studies

Kliimamuutuse mõju hindamine rannaniidu taimekooslusele mesokosmi katse ja mehitamata õhusõidukiga kogutud andmete põhjal

A Thesis for applying for the degree of Doctor of Philosophy in Environmental Protection.Väitekiri filosoofiadoktori kraadi taotlemiseks keskkonnakaitse erialal.Semi-natural grasslands are an essential part of the cultural landscape of Europe. Semi-natural grasslands are commonly characterised by a very high biodiversity, including rare species. Beyond the high biodiversity value, semi-natural grasslands worldwide provide many ecosystem services, including: carbon sequestration and storage, nutrient cycling, regulation of soil quality, habitats for migrating birds, erosion control, and flood regulation. Within the realm of semi-natural grasslands, coastal meadows are particularly important. However, coastal grasslands are threatened by a range of factors such as coastal squeeze, transformation into monoculture ponds, pollution, and climate change. Coastal areas are threatened at a range of spatial scales as a result of sea-level rise, and can include higher flooding frequency in coastal areas, salt water intrusion in aquifers, and potential declines in the extent of coastal wetlands. A warmer climate also implies a modification in precipitation patterns affecting runoff into the sea. In coastal areas, both water levels and salinity have a strong impact on species distribution and therefore on the structure and composition of aquatic and coastal floral and faunal communities. Consequently, plant communities in coastal meadows are expected to undergo changes in their composition and structure. The current thesis explores different methodologies to assess plant community distribution, above-ground biomass, and the effects of management type, duration, and intensity on sward structure using UAV-derived multispectral data and aerial photogrammetry. In addition, the keystone of this thesis is a mesocosm experiment that was used to assess shifts in species richness and abundance in plant community types in Estonian coastal meadows related to future change scenarios of water level and salinity for the Baltic Sea. a. Unmanned Aerial Vehicle (UAV) The use of UAV demonstrated to be able to identify plant community extent and distribution in high biodiversity value coastal meadows in West Estonia. Species diversity and biomass significantly influence the quality of data and this should be accounted for when planning the sample collection to achieve better results. This study has shown that UAVs are useful tools of mapping grasslands at a plant community level. Also, UAV showed to be possible to reveal the structure of the grassland and how it is affected by the management history. For example, the grassland turns more homogeneous under long-term monospecific grazing, b. Mesoscosm Experiment The mesocosm experiment in the present study revealed different temporal changes of wetland communities to altered salinity and water conditions, highlighting the response of plant species to environmental variables. These changes were not significant according to alteration of water level and salinity in the Open Pioneer community, but they were over time. On the other hand, Lower Shore and Upper Shore had significant changes according to time and treatments. These could be explained by dynamic differences in the communities, since Open Pioneer was more variable. c. Conclusions Both methodologies, remote sensing and the mesocosm experiment, are evidently important to evaluate the structure and function of Estonian coastal meadows. The mapping of the extent and structure of coastal plant communities allows an evaluation of the current state of the ecosystem. The mesocosm experiment helps to understand changes in plant community composition under altered conditions of water level and salinity in Estonian coastal meadows and consequently, understand how species richness, abundance, and biomass will respond to those changes. This information is important when considering the protection and potential management of these areas taking into account the species diversity of fauna and flora as well as that of livestock.Uuring viidi läbi kahel tasandil: uuringukohtades Lääne-Eestis ja katsekeskkonnas. Esimesel juhul valiti Silma looduskaitsealal, Matsalu rahvuspargis ja Vormsi saarel ranniku taimekoosluste ja maapealse biomassi kaardistamiseks kokku üheksa rannaniiduala (I, II). Teine osa hõlmab mesokosmi katset (III), mille käigus kasutati katse seadmiseks ja eksperimenteerimiseks Silma looduskaitsealalt kogutud proove. Vaatamata oma suhteliselt väikesele pindalale (45 228 km2) iseloomustab Eestit mitmekesine geoloogia, pinnamood ja kliima. Läänemere rannaniidud on tekkinud ja need säilivad maa isostaatilise tõusu, setete kogunemise ja alade vähese intensiivsusega majandamise – karjatamise või niitmise – tõttu. Eesti rannikumärgaladel on ebatavaline hüdroloogiline režiim. Kuna loodete ulatus on väga väike (~0,02 m), põhjustab rannaniitude üleujutusi valdavalt tsüklonaalne aktiivsus Põhja-Atlandil ja Fennoskandias. Üleujutuste sagedus ja ulatus on ebaregulaarne ning varieerub kogu rannikumaastikul, sõltudes tuule kiirusest ja suunast. Hiljutised hinnangud suhtelise meretaseme tõusu kohta kolmelt mõõnamõõturilt piki Eesti rannikut on järgmised: Tallinnas 1,5–1,7 mm a-1, Narva-Jõesuus 1,7–2,1 mm a-1 ja Pärnus 2,3–2,7 mm a-1 (Ward et al., 2014). Taimekoosluse klassifitseerimiseks ja biomassi prognoosimiseks analüüsiti üheksat rannikumärgala kolmes kohas Silma looduskaitsealal, kahes kohas Matsalu rahvuspargis ja neljas kohas Vormsi saarel. Neis kohtades esinevad kõik väitekirjas käsitletud taimekooslused. Uurimiskohtade taimekooslused liigitati vastavalt Burnside´i jt fütosotsioloogilisele klassifikatsioonile (2007): pilliroostik, võsasoo, madal rannik, kõrgrannik, pioneerliikidega paljakud, kõrgrohustu, võsa ja metsamaa. Võsasoo ning võsa ja metsamaa jäeti nende marginaalse esinemise tõttu uurimusest välja. Uurimistöö käigus tehti kaks erinevat analüüsi, kasutades UAV-ga kogutud multispektraal- ja rgb-fotosid. UAV multispektraalseid pilte kasutati taimekoosluste kaardistamiseks Silma looduskaitsealal Põhja-Tahu, Lõuna-Tahu ja Kudani rannaniidul (I). Järgnevalt kasutati multispektraalseid ja rgb-pilte kõrge ruumilise eraldusvõimega kaartide koostamiseks maapealse biomassi tuvastamiseks kõigis üheksas uuringukohas (II). Taimekoosluste kaardistamiseks (I) ja maapealse biomassi prognoosimiseks (II) kasutati otsustusmetsa klassifikatsiooni. Seejärel analüüsiti maapealse biomassi kaartide abil majandamisviisi ja intensiivsuse mõju rannaniitude heinamaade struktuurile (II). Teavet rannaniitude kasutusviisi kohta saadi maaomanikega isiklikult suheldes. Uurimistöö teises osas valiti mesokosmi katse jaoks kolm taimekooslust: pioneerliikidega paljakud, madal rannik ja kõrgrannik. Need kooslused valiti sealsete võtmeliikide spetsiifilise autökoloogilise kasvukohaeelistuse tõttu (nt soolsus ja mulla veesisaldus). Katsest välja jäetud pilliroostikus ja võsasoos domineerivad üleujutust taluvad liigid; kõrgrohustu kujutab endast maismaa ja märgalade ökosüsteemi vahelist kooslust, ning võsa on täielikult maismaa. Silma looduskaitsealal varuti Põhja-Tahu alalt 2018. aasta juunis kolmest valitud taimekooslusest 15 mätast (suurus 50 x 70 cm, paksus 30 cm). Mesokosmi katse varustus koosnes mahutitest (90L, mõõtmed 56 x 79 x 32 cm), mis olid täidetud 2:1:1 mullaseguga, mis koosneb pestud sõmera struktuuriga liivast, savist ja kompostist, mis on väga sarnane märgala põhjasubstraadiga. Mahutid numereeriti ja varustati vastava tähisega. Mahutid asusid kogu katse jooksul samal kohal. Katse käiku hinnati alalise gradueeritud 50 cm2 kvadraadi abil, mis jaotati 25 kvadraadiks (10 x 10 cm), ja määrati kindlaks muutused esinevate taimeliikide arvukuses pinnakatte pindala järgi (katteprotsent). Katse kestis kolme aastat veetaseme ja soolsuse tingimustes, mis tuletati kliimamuutuste prognoosidest 2100. aastaks. Liikide arvukus ja liigirikkus arvutati 2018., 2019. ja 2020. aastaks iga taimekoosluse kohta eraldi. Liigirikkuse erinevusi aastati ja kasvutingimuste suhtes hinnati Kruskal Wallise testiga, mis põhineb Bonferroni kohandustega Dunni testil, et tuvastada liigirikkuse erinevusi igal aastal. Liigilise arvukuse esitamiseks kasutati arvukuse kõveraid. Taimekoosluse koostise erinevuste uurimiseks kasutati permutatsioonilist mitmemõõtmelist analüüsi Bray-Curtise erinevusega. Aasta ristmõju analüüsis käsitleti töötlemisviisi fikseeritud mõju ja valimeid juhusliku mõjuna. Tulemused ja järeldused Rannaniitudel hinnati taimekoosluste levikut, maismaa biomassi ja taimestiku vertikaalset struktuuri. Fleissi kapa kordaja 0,89 põhjal kaardistati põhjalikult taimekooslused (I). Otsustusmetsa klassijärgsed vead näitavad, et homogeensema struktuuriga piirkondi on kergem klassifitseerida kui keerulise struktuuriga koosluseid. Otsustusmetsa algoritmi jõudlusanalüüs näitas, et biomassi hindamisel saadi parim tulemus, kui multispektraalne info kombineeriti fotogramm-meetriliselt loodud digitaalse maastikumudeliga (DTM, ingl digital terrain model) (II). Tulemused viitavad sellele, et mitme anduri kombinatsiooni saab kasutada ökosüsteemi omaduste mõõtmiseks, mida ainult spektraalinformatsiooni analüüsides ei pruugi tuvastada. Siinse uuringu maapealse biomassi prognooside suur täpsus näitab, et rannaniitude jälgimisel on kaugseire UAV-ga sobiv meetod. Struktuurianalüüsi tulemused näitasid, mil määral mõjutab biomassi jaotust karjatamise kestus ja heterogeensus. Pidevalt majandatavatele rohumaadele on iseloomulikud suuremad ja homogeensemad alad (II). Üldine lineaarne mudelianalüüs ja Mann-Whitney u-testid näitasid, kuidas taimtoidulised liigid mõjutavad rohumaa struktuuri. Rohumaad, millel karjatatakse erinevaid taimtoidulisi, on mitmekesisema struktuuriga kui veiste karjamaa (II). Mesokosmi katse tulemused näitasid, et kõigis kolmes Läänemere ranniku märgalade koosluses ilmnesid aja jooksul vee- ja soolsusrežiimis märkimisväärsed muutused, mis tõi esile taimeliikide reaktsiooni keskkonnamuutuste suhtes (III). Pioneerliikidega paljakutel suurenes liigirikkus ja taimkate kõigi keskkonnamuutuste korral, sellega võrreldes esines madalal rannikul ja kõrgrannikul nii veetaseme kui ka soolsusega seotud muutusi vähemal määral. Pioneerliikidega paljakuid mõjutab enamasti soolsus, seda isegi peamiselt sõmerast, keskmise fraktsiooniga ja peenest liivast koosnevas pinnases, mis säilitab vähem toitaineid kui peenema fraktsiooniga muld. Spergularia marina ja Glaux maritima aitasid kaasa liigirikkuse suurenemisele mulla suurenenud ja vähenenud soolsuse tingimustes. Üldiselt ei ilmnenud madala ranniku ja kõrgranniku taimekooslustes soolsuse muutumise korral olulisi muutusi võrreldes kontrollkatsega. Nendes kooslustes on liike, mis kasvavad nii soolases kui ka mittesoolases keskkonnas. Veetaseme muutus mõjutas pioneerliikidega paljakute taimekooslust sarnaselt soolsuse muutmisega. Selle koosluse liigirikkus suurenes kõrgema veetaseme korral, võrreldes kontrollkatsega. Kõrgema veetasemega kohanenud liike nagu Eleocharis palustris esines kõrgenenud veetaseme korral kolmandal aastal rohkem; alanenud vees leidus katse lõpus rohkem väiksema veevajadusega liike, nagu Glaux maritima ja Centaurium littorale. Madalal rannikul registreeriti madalama veetaseme korral liigirikkuse muutus, võrreldes kontrollkatsega. Aja jooksul toimuv liikide varieeruvus ilmnes vähese pinnakatvusega liikide puhul, nt ahenesid Carex flacca ja Triglochin palustris´e kasvukohad. Madal rannik asub veetasemelt pioneerliikidega paljaku ja kõrgranniku vahel ning see võib seletada, miks sealsed liigid taluvad mulla mitmesuguseid niiskustingimusi. Kõrgranniku koosluses vähenes kõrgenenud veetaseme korral liikide arv ja sellest tulenevalt ka liigirikkus; sealjuures laienesid vähese pinnakatvuse ja madala veetasemega kohastunud liikide Stellaria graminea ja Viola canina kasvukohad. See uurimus näitas, et ökoloogilistes uuringutes võib erinevate metoodikate kombinatsioon osutuda tõhusaks. Vaid vähestes uuringutes kombineeritakse ökosüsteemiprotsesside mõistmiseks erinevaid lähenemisviise, nt kaugseiret ja katseplatvorme, antud töös mesokosmi katset. Uued tehnoloogilised edusammud kaugseire vallas võivad lahendada küsimusi, millele vastuse leidmine traditsiooniliste ökoloogiliste meetodite abil oleks keeruline või ebapraktiline. Samas on traditsioonilise lähenemisviisiga, nt mesokosmi katsega saadud teadmised uue tehnoloogilise potentsiaali rakendamiseks väga vajalikud. Uurimus näitas, et UAV on sobiv vahend rannikurohumaade struktuuri ja taimekoosluste leviku täpse eraldusvõimega kaartide koostamiseks. Teisest küljest aitab mesokosmi katse mõista taimekoosluse koostise muutusi eri veetaseme ja soolsuse tingimustes.Publication of this thesis is supported by the Estonian University of Life Sciences and by the Doctoral School of Earth Sciences and Ecology created under the auspices of the European Social Fund

Satellite-based Machine Learning modelling of Ecosystem Services indicators: A review and meta-analysis

Satellite-based Machine Learning (ML) modelling has emerged as a powerful tool to understand and quantify spatial relationships between landscape dynamics, biophysical variables and natural stocks. Ecosystem Services indicators (ESi) provide qualitative and quantitative information aiding the assessment of ecosystems’ status. Through a systematic meta-analysis following the PRISMA guidelines, studies from one decade (2012–2022) were analyzed and synthesized. The results indicated that Random Forest emerged as the most frequently utilized ML algorithm, while Landsat missions stood out as the primary source of Satellite Earth Observation (SEO) data. Nonetheless, authors favoured Sentinel-2 due to its superior spatial, spectral, and temporal resolution. While 30% of the examined studies focused on modelling proxies of climate regulation services, assessments of natural stocks such as biomass, water, food production, and raw materials were also frequently applied. Meta-analysis illustrated the utilization of classification and regression tasks in estimating measurements of ecosystems' extent and conditions and findings underscored the connections between established methods and their replication. This study offers current perspectives on existing satellite-based approaches, contributing to the ongoing efforts to employ ML and artificial intelligence for unveiling the potential of SEO data and technologies in modelling ESi.info:eu-repo/semantics/publishedVersio

Remote Sensing in Mangroves

The book highlights recent advancements in the mapping and monitoring of mangrove forests using earth observation satellite data. New and historical satellite data and aerial photographs have been used to map the extent, change and bio-physical parameters, such as phenology and biomass. Research was conducted in different parts of the world. Knowledge and understanding gained from this book can be used for the sustainable management of mangrove forests of the worl

The effects of elevated CO2 and eutrophication on surface elevation gain in a European salt marsh.

Salt marshes can play a vital role in mitigating the effects of global environmental change by dissipating incident storm wave energy and, through accretion, tracking increasing water depths consequent upon sea level rise. Atmospheric CO2 concentrations and nutrient availability are two key variables that can affect the biological processes that contribute to marsh surface elevation gain. We measured the effects of CO2 concentrations and nutrient availability on surface elevation change in intact mixed-species blocks of UK salt marsh using six open-top chambers receiving CO2 -enriched (800 ppm) or ambient (400 ppm) air. We found more rapid surface elevation gain in elevated CO2 conditions: an average increase of 3.4 mm over the growing season relative to ambient CO2 . Boosted regression analysis to determine the relative influence of different parameters on elevation change identified that a 10% reduction in microbial activity in elevated CO2 -grown blocks had a positive influence on elevation. The biomass of Puccinellia maritima also had a positive influence on elevation, while other salt marsh species (e.g. Suaeda maritima) had no influence or a negative impact on elevation. Reduced rates of water use by the vegetation in the high CO2 treatment could be contributing to elevation gain, either directly through reduced soil shrinkage or indirectly by decreasing microbial respiration rates due to lower redox levels in the soil. Eutrophication did not influence elevation change in either CO2 treatment despite doubling aboveground biomass. The role of belowground processes (transpiration, root growth and decomposition) in the vertical adjustment of European salt marshes, which are primarily minerogenic in composition, could increase as atmospheric CO2 concentrations rise and should be considered in future wetland models for the region. Elevated CO2 conditions could enhance resilience in vulnerable systems such as those with low mineral sediment supply or where migration upwards within the tidal frame is constrained.Marie Curie Incoming International Fellowship (Grant ID: FP7-PEOPLE-IIF 623720 STORM)This is the author accepted manuscript. The final version is available from Wiley via https://doi.org/10.1111/gcb.1339

Toward a Coordinated Global Observing System for Seagrasses and Marine Macroalgae

In coastal waters around the world, the dominant primary producers are benthic macrophytes, including seagrasses and macroalgae, that provide habitat structure and food for diverse and abundant biological communities and drive ecosystem processes. Seagrass meadows and macroalgal forests play key roles for coastal societies, contributing to fishery yields, storm protection, biogeochemical cycling and storage, and important cultural values. These socio-economically valuable services are threatened worldwide by human activities, with substantial areas of seagrass and macroalgal forests lost over the last half-century. Tracking the status and trends in marine macrophyte cover and quality is an emerging priority for ocean and coastal management, but doing so has been challenged by limited coordination across the numerous efforts to monitor macrophytes, which vary widely in goals, methodologies, scales, capacity, governance approaches, and data availability. Here, we present a consensus assessment and recommendations on the current state of and opportunities for advancing global marine macrophyte observations, integrating contributions from a community of researchers with broad geographic and disciplinary expertise. With the increasing scale of human impacts, the time is ripe to harmonize marine macrophyte observations by building on existing networks and identifying a core set of common metrics and approaches in sampling design, field measurements, governance, capacity building, and data management. We recommend a tiered observation system, with improvement of remote sensing and remote underwater imaging to expand capacity to capture broad-scale extent at intervals of several years, coordinated with stratified in situ sampling annually to characterize the key variables of cover and taxonomic or functional group composition, and to provide ground-truth. A robust networked system of macrophyte observations will be facilitated by establishing best practices, including standard protocols, documentation, and sharing of resources at all stages of workflow, and secure archiving of open-access data. Because such a network is necessarily distributed, sustaining it depends on close engagement of local stakeholders and focusing on building and long-term maintenance of local capacity, particularly in the developing world. Realizing these recommendations will produce more effective, efficient, and responsive observing, a more accurate global picture of change in vegetated coastal systems, and stronger international capacity for sustaining observations