The research team, led by Sunbowen Zhang of Fujian Normal University together with colleagues including Chaobin Xu, Linsheng Wen, Quanlin Zhong, and Baoyin Li, set out to address a persistent blind spot in carbon accounting. Most previous studies of regional carbon budgets have operated at national, provincial, or urban-agglomeration scales, or have considered only a single ecosystem type such as cropland, forest, or grassland. County-level analysis, which captures the scale at which land-use decisions and industrial policy actually play out, has remained comparatively rare. By building an accounting framework that integrates multiple vegetation carbon sinks with a full inventory of anthropogenic emissions, the authors argue that their approach corrects a systematic bias embedded in earlier single-ecosystem methods.

The technical machinery behind the study is ambitious. Carbon emissions were drawn not from provincial statistics but from the EDGAR 2024 gridded greenhouse gas dataset, which compiles emissions of carbon dioxide, methane, nitrous oxide, and fluorinated gases in CO2-equivalent terms using Global Warming Potential values from the IPCC Fifth Assessment Report. Emissions for each county were extracted by spatially overlaying administrative boundary vectors onto the emission grid and aggregating all grid cells within each jurisdiction. Carbon sequestration, by contrast, was estimated from NASA’s MOD17A3 net primary productivity data at 500-meter resolution, applying the standard photosynthetic conversion factor: for every gram of dry plant matter produced, 1.63 grams of CO2 are absorbed from the atmosphere. Land-cover inputs came from the 30-meter China Land Cover Dataset spanning 2000 to 2023, with all administrative boundaries harmonized to a 2020 standard.

From these raw fluxes the team computed three diagnostic indicators for each county. The carbon compensation rate (CCR) divides sequestration by emissions: a value above 1 marks a net carbon sink, below 1 a net source. The economic contribution coefficient (ECC) measures carbon productivity, comparing a county’s share of provincial GDP with its share of provincial emissions; values above 1 indicate efficient, low-carbon economies. The ecological support coefficient (ESC) characterizes carbon sink capacity relative to both the province and each county’s emission share. Kernel density estimation using the Epanechnikov function traced how the distributions of emissions and sequestration evolved over time, while the natural breaks method classified counties into five tiers for visualization.

The emission findings follow a familiar but instructive arc. Province-wide emissions climbed rapidly from 2000 to 2011, then decelerated after 2012, a shift the authors link to China’s strategic pivot toward ecological civilization and green development. A pronounced surge in 2010 and 2011 coincides with the establishment of the West Coast Economic Zone in March 2011, which spurred waves of industrial investment. Spatially, the pattern was remarkably stable throughout: coastal counties such as Xiamen and Shishi occupied the highest emission tiers year after year, while inland counties like Pingnan stayed consistently low. Kernel density curves shifted steadily rightward and broadened, showing both rising average emissions and growing divergence between high-emitting and low-emitting counties, though the persistent unimodal shape indicates most counties remained clustered around the evolving provincial peak.

Carbon sequestration told the mirror-image story. Mountainous inland counties, particularly Nanping, Longyan, and Sanming, recorded the province’s highest sequestration throughout the period, while industrialized coastal areas showed markedly lower values. The highest county-level sequestration in 2023 was found in Jianou City, Nanping, at 5.32 million tons, an increase of 8.8 percent over 2000. The team attributes this strengthening partly to Fujian’s designation as a national ecological civilization pilot zone in 2016 and associated restoration programs, such as Ningde’s ‘Four Forests’ initiatives, which expanded vegetation cover in Shouning and Zhouning counties. The authors caution, however, that their framework cannot disentangle the effects of human intervention from climate variability, and that the explanatory conclusions remain hypothetical rather than causally verified.

The carbon compensation rate crystallized the province’s imbalance. Province-wide CCR fell from roughly 2.23 in 2000 to about 0.62 in 2023, meaning Fujian’s sinks now cover well under half of its emissions. Inland counties posted extraordinary values: in 2003, Yongtai reached 32.27, Pingnan 30.72, and Mingxi 27.93, while coastal urban districts such as Changle (0.09), the Zhangzhou urban area (0.12), and the Fuzhou urban area (0.16) sat near zero. By 2023, Pingnan still led at 18.86 while Shishi had fallen to 0.006. Nanping City consistently recorded the highest prefecture-level CCR, peaking at 4.33 in 2001 on the strength of extensive forest cover and a less industrialized economy, whereas the special economic zone of Xiamen remained the lowest throughout. The northwest-southeast gradient, forested sinks inland and industrial sources on the coast, proved remarkably durable over 24 years.

The study’s most policy-relevant contribution is its zoning framework, which fuses carbon budget indicators with China’s major function-oriented zones (MFOZs), the government-delineated categories that assign each territory a core development function. Using ECC and ESC thresholds, the researchers classified all counties into four primary carbon balance zones: carbon neutrality demonstration zones (high economic efficiency and strong sinks), carbon sink conservation zones (weak economies but valuable sinks needing protection), industrial decarbonization transition zones (efficient economies on high-carbon industries with inadequate ecological restoration), and low-carbon revitalization collaboration zones lagging on both dimensions. Cross-referencing with MFOZ designations yielded nine refined subzones, ranging from low-carbon development zones in agricultural counties such as those of Nanping and Sanming, home to specialty products like Ninghua rice and Jianning white lotus, to carbon source control zones concentrated in the urban cores of Fuzhou, Xiamen, and Quanzhou, where labor-intensive manufacturing such as Jinjiang’s footwear and garment industry drives substantial emissions.

The authors translate this typology into a differentiated governance agenda. Coastal economic cores should face the strictest caps on construction land and emission intensity, mandatory green industrial transformation, and exploration of cross-county carbon trading and compensation mechanisms within the Fuzhou-Putian-Quanzhou corridor. Northwestern and southwestern sink strongholds such as Shanghang, Wuping, Zhangping, and Jian’ou should have their carbon sink capacity formally incorporated into regional carbon neutrality accounting, with enhanced ecological compensation for demonstration counties like Zherong and Shouning. Inland areas are advised to avoid replicating coastal high-carbon pathways, instead developing ecotourism, under-forest economies, and low-carbon agriculture, while agricultural modernization in zones such as Changtai, a provincial modern agricultural industrial park since 2019, must guard against rising farm emissions. The team also stresses dynamic monitoring: regular updates of emission, sequestration, ECC, and ESC data to adjust zone boundaries as conditions change.

The study is candid about its limits. All interpretations of driving mechanisms rest on descriptive spatiotemporal correlation rather than rigorous causal identification; the indicator system cannot eliminate confounding factors, and the observed link between economic gradients and zoning patterns should be read as a descriptive typology, not a causal model. The authors propose that future work apply quasi-experimental designs, including difference-in-differences, event studies, and instrumental variable models, to separate the net effects of ecological policy, industrial transformation, and land-use change. Even so, the MFOZ-coupled framework offers what the researchers describe as a replicable analytical paradigm for other provincial ecological civilization pilot zones, and a scientific foundation for reconciling the enduring tension between Fujian’s factory coast and its forested interior.

Subject of Research: County-level carbon budget spatiotemporal patterns and carbon balance zoning optimization in Fujian Province, China

Article Title: Spatiotemporal patterns and carbon balance zoning optimization of county-level carbon budget in Fujian Province

Article References: Zhang, S., Xu, C., Wen, L., Zhong, Q., Hu, Q., Li, B., & Chen, B. (2026). Spatiotemporal patterns and carbon balance zoning optimization of county-level carbon budget in Fujian Province. iScience, 29(10), Article 117233. https://doi.org/10.1016/j.isci.2026.117233

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.117233

Keywords: carbon budget, carbon sequestration, carbon emissions, Fujian Province, carbon balance zoning, major function-oriented zones, net primary productivity, EDGAR, ecological civilization, spatial governance, carbon neutrality, county-level analysis