DOI: 10.5061/dryad.r7sqv9ssc
title: Data from: Comparing passive and active kelp restoration techniques along an urbanised coast

description: Kelp forests have received increasing attention due to widespread declines
 in many regions, alongside stability or expansions in others, and the
 potential to reverse loss where it has occurred. Such reversal requires
 understanding which techniques of intervention can restore their coverage
 at large scales in cost-effective ways. We investigated two techniques of
 kelp forest restoration along a metropolitan coast in southern Australia:
 ‘passive’ restoration, involving seascape-scale improvements to water
 quality for multi-species restoration of kelp forests and seagrass
 meadows, and ‘active’ restoration, which involves local-scale kelp
 transplants to restore kelp forests. Passive restoration through
 water quality improvements (i.e., wastewater treatment plant upgrades)
 over 10 years yielded kelp recovery of 1.15 hectares. Active restoration
 through transplanting local 1 m2 patches of kelp over 3 years yielded
 0.0008 hectares. While each technique produced next-generation recruits to
 sustain canopies, the annual rate of kelp expansion was ~386 times greater
 via passive restoration than active restoration. The passive
 approach required considerable initial investments and political will;
 however, the cost per hectare (~USD$ 42,250 ha -1) is substantially lower
 compared to the active approach of transplanting kelp (~USD$ 292,915 ha
 -1), which appears to be a riskier process with lower returns on financial
 investment. Passive restoration through water quality improvements
 facilitates substantial kelp gains, offers increased scalability, and
 provides broader ecosystem benefits across seascape scales, though the
 initial investment required is substantial. Active restoration may provide
 immediate canopies of kelp through transplantation, but provides a
 negligible increase in kelp cover over time. Funding for upscaling remains
 a significant limitation. The effectiveness of each restoration technique
 depends on the local coastal ecology, with passive methods offering
 benefits at broader spatial scales and active methods providing more
 immediate results. However, sustained and large-scale recovery of kelp
 ecosystems appears to require thoughtful approaches that directly address
 the underlying drivers of coastal degradation.
description: Data file for JAPPL-2025-00866 # Data from: Comparing passive and active
 kelp restoration techniques along an urbanised coast Journal of
 publication: *Journal of Applied Ecology* Corresponding author:
 [sean.connell@adelaide.edu.au](mailto:sean.connell@adelaide.edu.au) ###
 DATA AND FILE OVERVIEW This data relates to measurements of kelp forest
 recovery associated with two restoration approaches: passive restoration
 via water quality improvements and active restoration via kelp
 transplantation, along an urbanised coastline in southern Australia. Data
 include estimates of percent kelp cover and turf cover collected from
 field surveys between 2007 and 2025, as well as mapped reef areas. Passive
 restoration data quantify changes in kelp cover derived from
 transect-based habitat surveys across multiple reef sites. Active
 restoration data quantify changes in kelp cover based on the mapped area
 of individual transplanted kelp patches, converted to percentage cover
 relative to the total reef area. The dataset is used to compare the
 magnitude, rate, and cost-effectiveness of kelp recovery under passive and
 active restoration strategies at differing spatial and temporal scales.
 ### DESCRIPTION OF VARIABLES * Site: Name or identifier of the reef site
 where restoration techniques were assessed. Time: sampling period relative
 to restoration (pre or post). * Treatment: restoration approach assessed
 at the site (passive or active). * Monospecific_kelp_cover_percent:
 percent cover of monospecific kelp relative to total reef area. Kelp cover
 at passive restoration sites was derived from transect-based habitat
 surveys. Kelp cover at active restoration sites was estimated by measuring
 the area of individual kelp patches and converting this to percent reef
 cover using mapped reef area. * Turf_cover_percent: percent cover of turf
 algae relative to total reef area. Data were derived from transect-based
 habitat surveys. Turf cover was only quantified at passive restoration
 sites; therefore, turf cover values are reported as NA for active
 restoration sites. * Reef_area_ha: mapped area of the reef site in
 hectares (ha).