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Article
<br /> a Hawaiian Islands G
<br /> •
<br /> Pacific II
<br /> Ocean
<br /> Study 11 11
<br /> ILL
<br /> region Human Urban Wastewater Nutrient Sediment Peak Wave
<br /> population A runoff A pollution A loading A input A rainfall A exposure A
<br /> b 'Upolu Point
<br /> O
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<br /> 16 110 ¢ 110 _
<br /> 120
<br /> 126 —
<br /> "rry 130 _ _
<br /> 130+ — — '
<br /> 140
<br /> 140• 150
<br /> 150 160 —_
<br /> A 160 170
<br /> N 170 180 ,
<br /> Oh 5 10 km 1 aSouth Point
<br /> .�O ry0,50 a0,,c0 O .�O 'o ,50 tp O ry00 000 000 ry,,c0 O .�6 6b dab ry,,o6 O ry%o�00 ryryo�O O .�O ry0 00 tp O ryo,,c0 INQ� �ryo
<br /> 5.
<br /> Number of people Area Total effluent Total nitrogen Sediment Rainfall Wave power
<br /> (101 within 15 km) (101 mz ha-1) (1011 ha-1) (kg ha-1) (101 kg ha-1) (101 m3 ha-1) (kW m 1)
<br /> Permanent reef survey locations
<br /> • Predisturbance Year I I I I I I I I I
<br /> O '� `L O b h 60 A O '� `L O b h 6 O O Temporal change d
<br /> O Response to stdi marine heatwave O O ell
<br /> O ell,
<br /> O O O O � '� � '� '� '� '�
<br /> ry0 ry0 ry0 ry0 ry0 ry0 ry0 le,ry0 ry0 ry0 ry0 ry0 ry0 ry0 ry0 ry0 ry0 ry0 ry0 Decrease ® ®Increase
<br /> O Four years postdisturbance i ii ii i
<br /> Permanent reef survey data availability Predisturbance Disturbance Postdisturbance
<br /> Fig.11 Select local land-sea human impacts and environmental factors on blue hues indicating decreases and red hues indicating increases.Change is
<br /> coral reefs in our study region in Hawai'i.a,Geographic location of the based on the mean difference between the first5 years(2000-2004)and the
<br /> Hawaiian Islands.b,Study region with reefsurveys shown for the following: most recentS years(2015-2019)in the time series.This accounted for year-to-year
<br /> reef trajectories predisturbance(n=23;Fig.2),coraI response tot he2015 variabi I ity in the epi sod ic nature of factors such as wave exposure,rainfa I I and
<br /> marine he atwave(n=80;Fig.3)and cora I reefs four years postdisturbance sediment input.A subset of factors is shown inc owing to space constraints.
<br /> (n=55;Fig.4).c,Spatial distribution in annual,high-resolution(100m)data on Additional factors(not shown)include annual rainfal I,phytoplankton biomass,
<br /> local human impacts and environmenta I factors from 2000 to 2019(coloured ocean tempe rat ure(mean and variabiIity),heat stress,irradiance,fish inggear
<br /> lines).They axis represents distance along the coastline in kilometres from restrictions,depth and metrics offish biomass.The distribution,change
<br /> north to south aIongthe study region inb.Vert icaI bar represents the change overtime and variability of all factors are shown in Supplementary Fig.1.
<br /> overtime(A)for each 100 m section along the coast.A changeover time is high See Extended Data Table land Supplementary Information for detailed
<br /> (H,d>-50%),moderate(M,0>d<50%)or there isno change(NC,grey),with information on loca I land-sea human impacts and environmentaIfactors.
<br /> such as population density`and reef accessibility2b,or composite Hawaiian Islands(Extended Data Fig.2).We quantified drivers of coral
<br /> indices such as'water quality'"that can be affected by anything from reef benthic change atthe scale of individual reefs over 12 years before
<br /> deforestation 2'toaquaculture28.Such proxiesdo not identifythepolicy disturbance(2003-2014),during and immediately following the marine
<br /> levers local resource managers can pull and are less likely to result in heatwave(2014-2016)andfouryears postdisturbance(2016-2019).Our
<br /> management actions or successful conservation outcomes. findings show that simultaneously mitigating local human impacts on
<br /> Here we present a unique 20-year time series of land-sea human both landand seasupports positivecoral cover trajectories in theabsence
<br /> impacts and environmental factors known to affect coral reef ecosys- of periodic acute disturbance,reduces coral loss during a marine heat-
<br /> tem processes across our study region in the Hawaiian Islands(Fig.la). wave and promotes coral reef persistence following severe heat stress.
<br /> Human factors include urban runoff,wastewater pollution,nutrient
<br /> loading,sediment input and local restrictions on types offishinggear.
<br /> Environmental factors include peakand annual rainfall,wave exposure, Reef trajectories predisturbance
<br /> variability in ocean temperatures and heat stress,irradianceand phyto- Coral cover among reefs surveyed in 2003 was 36.9±2.3%(mean±s.e.;
<br /> plankton biomass.We also incorporate multiple fish biomass metrics n=23)and changed byless than 3%in the subsequentyears leading up
<br /> that represent the critical role reef fish play in maintaining coral reef to the2015 marine heatwave(Fig.2a).However,coral cover trajectories
<br /> ecosystem function"'(see Extended Data Table 1 for a full list of on individual reefs varied considerably over this time period:44%of
<br /> factors).Wecombined thisdatasetwith recurring,permanently marked reefs showed a positive trajectory(that is,increased coral cover),35%
<br /> and site-specific underwater survey data on coral reef benthiccommuni- of reefs showed a negative trajectory(that is,decreased coral cover)
<br /> ties(Fig.1b).Our study reefs spanned large spatiotemporal gradients and the remaining reefs showed no change(Fig.2b).To the best ofour
<br /> inland-sea human impactsand environmental factors(Fig.1c)that are knowledge,no acute disturbance occurred that can explain thesediver-
<br /> comparable to coral reef ecosystems globally(Extended Data Fig.1),and gent trajectories.Yet,we did find distinct differences in local conditions
<br /> which experienced the most severe marine heatwave on record in the between positive and negative trajectory reefs in the years before and
<br /> 2 1 Nature I www.nature.com
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