Water regulation is one of the least visible yet most consequential services that ecosystems provide. Forested slopes intercept rainfall, slow surface runoff, and encourage infiltration into soils and aquifers, which in turn sustains baseflow in rivers during dry seasons and buffers downstream communities against floods and landslides. When forests are cleared for agriculture, plantations, or settlements, the landscape loses much of this sponge-like behavior. Rainfall that once soaked gradually into the ground instead races over compacted surfaces, carrying topsoil with it, swelling rivers quickly, and leaving less water stored for the months when it is needed most. Sulawesi, with its rugged central highlands, four peninsulas, and dense network of small watersheds, is particularly sensitive to these shifts because so many communities depend on short, steep catchments for irrigation and drinking water.

To capture this capacity spatially, the study employed a weighted spatial index built on a Simple Additive Weighting approach, a multi-criteria decision technique that combines several input layers into a single score. In this case, the layers included natural landscape characteristics, natural vegetation, and land cover data for each of the three reference years. Each land cover type was assigned a weight reflecting its contribution to water regulation, so that intact natural forest scored highest, while agricultural land and built-up areas scored progressively lower. The weighted layers were then summed to produce a continuous index of potential water regulation capacity, which was classified into categories ranging from very high to very low. This approach allowed the author to compare like with like across a 32-year span and to pinpoint where on the island the losses were concentrated.

The results reveal a clear geographic pattern of decline. Central Sulawesi and South Sulawesi contributed most strongly to the reduction in high-capacity areas, consistent with the intensive forest conversion and agricultural expansion that have characterized those provinces in recent decades. South Sulawesi, home to the densely populated southwestern lowlands and the Makassar urban corridor, has long experienced pressure from rice cultivation, cocoa and other perennial crops, and urban growth. Central Sulawesi has seen extensive land clearing linked to agriculture and, in some areas, plantation development. By contrast, Southeast Sulawesi and North Sulawesi showed partial recovery of high-capacity classes in the later period, suggesting that regrowth of secondary vegetation, protection efforts, or shifts in land management may have locally restored some regulatory function even as the island-wide trend remained negative.

Underlying these capacity changes is a fundamental shift in what covers the land. The study found that vegetated land cover types that strongly support water regulation declined from 75 percent of the island in 1990 to 54 percent in 2022. That is a loss of roughly a fifth of the island’s vegetated surface in a single generation, largely driven by conversion to agricultural and built-up areas. The magnitude of this transition matters because the relationship between vegetation and water regulation is not linear at the margins. Small losses of forest in headwater zones can disproportionately affect downstream flow regimes, and once soils are degraded, the hydrological functions they supported can take decades to recover even if vegetation returns.

The spatial heterogeneity that the study documents is itself scientifically important. Sulawesi is not losing its water regulation capacity uniformly; it is losing it in patches, corridors, and hotspots that correspond to provincial boundaries, watershed networks, and the geography of agricultural frontiers. This heterogeneity is precisely what makes the mapping approach valuable for policy. Rather than treating the island as a single unit with a single trend, the weighted index produces provincial- and watershed-level hotspots where the decline is most acute, and therefore where interventions such as forest protection, restoration, and ecosystem service-based zoning could be prioritized with the greatest expected benefit. In practical terms, a watershed whose index has slipped from high to moderate is a candidate for targeted restoration of riparian buffers and headwater forest, while a province showing widespread contraction of high-capacity classes may warrant stronger land use controls.

The study’s methodology also illustrates a broader trend in ecosystem service science: the use of relatively simple, transparent, and repeatable indices rather than data-hungry process models. Complex hydrological simulations can capture the physics of rainfall-runoff partitioning in detail, but they demand extensive calibration data that are often unavailable in tropical regions. A Simple Additive Weighting index, by contrast, requires only consistent land cover and landscape datasets, which are increasingly available from national mapping agencies and satellite programs. The trade-off is that the index measures potential capacity rather than actual water fluxes; it indicates where the landscape is structurally capable of supporting rainfall retention, baseflow, and watershed resilience, not how many cubic meters of water are being stored in any given year. For regional planning purposes, however, this potential-based framing is often exactly what is needed, because it identifies where the hydrological infrastructure of the landscape is being dismantled before the consequences appear in stream gauges.

The findings sit within a wider body of evidence on deforestation in Indonesia and its consequences. Sulawesi has been identified in previous research as a priority island for conservation because of its exceptional endemism and the rapid loss of its forests, with documented impacts on primate habitat and unique ecosystems. Studies of deforestation patterns in Sulawesi between 1990 and 2018 have shown persistent pressure on forest cover, and work on mangrove decline in South Sulawesi has highlighted how coastal ecosystem services have been degraded alongside terrestrial ones. The new analysis extends this picture into the hydrological domain, showing that the same land conversion processes that threaten biodiversity are also dismantling the island’s capacity to regulate water, with direct implications for flood risk, dry-season water supply, and agricultural stability for millions of people.

What makes the study particularly timely is the policy context. Indonesia has experimented with forest moratoria, peatland protection, and payment-for-ecosystem-service schemes, and researchers have debated how cost-effective these instruments are in reducing emissions and protecting services. Mapping exercises like this one provide the spatial evidence base that such policies require. If restoration funds are limited, they should flow to the watersheds where the loss of regulation capacity is steepest and where downstream exposure is greatest. The study’s outputs, which identify provincial- and watershed-level hotspots, are designed to support exactly that kind of prioritization, and the author notes that they could inform ecosystem service-based zoning as part of provincial spatial planning.

There are also lessons here for how tropical islands elsewhere are monitored. Sulawesi’s story, a 15-percentage-point decline in high-capacity land over three decades, driven overwhelmingly by the replacement of vegetation with agriculture and settlements, is a pattern that repeats across Southeast Asia, Madagascar, the Caribbean, and many other island systems where steep terrain concentrates both water services and land use pressure. The demonstration that a weighted spatial index built from freely available land cover data can track these changes consistently over more than three decades offers a template for other data-limited regions. As climate change intensifies both droughts and extreme rainfall in the tropics, the landscapes that quietly regulate water are becoming more valuable, not less. Sulawesi’s shrinking high-capacity core is a quantitative reminder that this natural infrastructure is finite, spatially specific, and, once lost, slow and expensive to rebuild.

Subject of Research: Land cover change and water regulation ecosystem services on Sulawesi Island, Indonesia

Article Title: Spatial heterogeneity of landscapes and land cover in Sulawesi Island in relation to water regulation ecosystem services

Article References: Nursaputra, M. (2026). Spatial heterogeneity of landscapes and land cover in Sulawesi Island in relation to water regulation ecosystem services. Environmental Monitoring and Assessment, 198(10), Article 1086. https://doi.org/10.1007/s10661-026-15892-z

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15892-z

Keywords: ecosystem services, water regulation, land cover change, spatial heterogeneity, Sulawesi Island, deforestation, Simple Additive Weighting, watershed resilience, forest restoration, Indonesia, landscape ecology, remote sensing

The origins of the contamination are more varied than most consumers assume. Microplastics in bottled water arise primarily from the degradation of polyethylene terephthalate, or PET, the polymer used to make most single-use bottles, as well as from the bottling process itself. Mechanical stress on bottles, exposure to sunlight, and freezing can all accelerate the shedding of particles into the water they contain, a phenomenon documented in studies that subjected bottles to squeezing, UV radiation, and temperature cycling. But the packaging is not the only culprit. Source water can carry plastic particles into the bottle before it is ever sealed, and storage conditions during transport and warehousing add further opportunities for degradation and release. The result is a complex mixture of particle types, sizes, and polymer compositions that differs from brand to brand and region to region, complicating any attempt to draw general conclusions about exposure levels.

The scale of the contamination varies enormously across the literature. Reported concentrations of microplastics in bottled water range from just a few particles per litre to thousands of particles per litre, depending on the brand, the geographical region where the water was sampled, and, critically, the analytical method used to count the particles. Studies that pushed detection down to smaller size fractions consistently found more particles, which suggests that much of the contamination lies below the size thresholds of older techniques. Research using surface-enhanced Raman spectroscopy has even identified PET nanoplastics in commercially bottled drinking water, confirming that particles small enough to interact with biological structures at the cellular level are present in products consumed by millions of people every day. This size dependence is one of the most important and unsettling patterns in the field: the smaller the particles researchers look for, the more of them they find.

Detecting and identifying these particles is itself a formidable technical challenge. The review identifies micro-Raman spectroscopy and micro-Fourier transform infrared spectroscopy, known as µRaman and µFT-IR, as the most reliable techniques currently available, because they can identify the polymer composition of individual particles through their characteristic vibrational spectra. Yet the two methods differ in their sensitivity to different size ranges, and both require extensive sample preparation to remove organic matter that can interfere with spectral readings. More advanced approaches are emerging, including stimulated Raman scattering microscopy, which enables rapid single-particle chemical imaging of nanoplastics, and surface-enhanced Raman spectroscopy, which amplifies the signal from particles too small for conventional methods. The fundamental problem, however, is not the absence of good instruments but the absence of standardization. Analytical protocols vary between laboratories, detection limits differ from study to study, and until recently there were no certified reference materials against which methods could be validated, making it extremely difficult to compare results across studies or to pool them into reliable exposure estimates.

The health implications hinge on particle size. Microplastics larger than a few micrometres are generally thought to pass through the digestive tract without crossing biological barriers, although they may still cause local effects in the gut. Nanoplastics, defined in the review as particles smaller than 100 nanometres, are a different matter entirely. At these dimensions, particles can penetrate biological barriers that would exclude larger material, raising concerns about oxidative stress, mitochondrial dysfunction, inflammation, carcinogenicity, immune disruption, and bioaccumulation in tissues. Laboratory studies have begun to map these mechanisms in detail. Experiments on human cell lines have shown that polystyrene microplastics alter the morphology, proliferation, and metabolism of kidney and liver cells, while meta-analyses of cytotoxicity data in intestinal cell models have helped clarify dose-response relationships. In animal models, microplastic exposure has been linked to intestinal damage, gut microbiota dysbiosis, hepatic lipid metabolism disorders, and elevated oxidative stress, painting a consistent picture of biological disruption across organ systems.

Epidemiological clues are also accumulating, though they remain preliminary. One striking finding cited in the review is the detection of higher numbers of microplastics in tumoral colon tissue from patients with colorectal adenocarcinoma compared with healthy tissue, an association that demands further investigation but underscores how readily these particles embed themselves in human tissue. Researchers are developing biomarkers of oxidative stress, inflammation, and genotoxicity to assess exposure to micro- and nanoplastics in human populations, an essential step toward moving from cell culture and animal studies to evidence of actual harm in people. The review is careful to note that uncertainties remain about chronic health effects, and that the lack of standardized exposure data is itself a barrier to epidemiology: without comparable measurements of what people are actually ingesting, it is difficult to test whether exposure correlates with disease outcomes.

There is also a chemical dimension to the hazard. Plastic particles do not travel alone. They carry chemical additives incorporated during manufacturing, such as plasticizers and stabilizers, and their hydrophobic surfaces adsorb organic and inorganic pollutants from the surrounding environment, a phenomenon often described as the Trojan horse effect. Trace metals, persistent organic pollutants, and other contaminants can hitch a ride on plastic particles and be delivered to biological tissues when the particles are ingested. This means that the toxicological risk of a plastic particle is not simply the risk of the polymer itself but the risk of the entire chemical payload it carries, a complexity that standard toxicity testing has only begun to address. For bottled water, where the particles originate largely from the packaging, the additive burden may differ from that of environmental microplastics, adding another layer of variability to the risk assessment.

The ecological consequences extend well beyond the human body. The review documents how microplastics disrupt aquatic ecosystems and biodiversity, with documented effects ranging from intestinal damage in zebrafish and nematodes to suppressed immune function and stress responses in corals. Because bottled water is a product of the same global plastic economy that pollutes rivers and oceans, the contamination of drinking water and the degradation of ecosystems are two faces of a single problem. Global plastic emissions continue to rise, and while microbial and enzymatic degradation of plastics offers a promising avenue for recycling and remediation, including engineered bacteria and enzymes that can break down PET, these technologies remain far from sufficient to stem the tide of particles entering the environment and, ultimately, the food and water supply.

Regulators are beginning to respond, but unevenly. The World Health Organization issued a landmark analysis of microplastics in drinking water in 2019, and the European Commission adopted a delegated decision in 2024 laying down a methodology for measuring microplastics in water intended for human consumption, a crucial step toward harmonized monitoring under the EU drinking water directive. The European Commission’s Joint Research Centre has since developed certified reference materials for microplastics in water, addressing one of the field’s most persistent gaps. In the United States, the Environmental Protection Agency has published a microplastics research strategy, and the National Institute of Standards and Technology runs a dedicated measurement science program for micro- and nanoplastics. The International Organization for Standardization has issued technical guidance on environmental plastics, and India has amended its plastic waste management rules, while the United Nations Environment Programme continues to push for a global framework to end plastic pollution. Yet the review emphasizes that a globally harmonized regulatory framework for micro- and nanoplastics in bottled water specifically remains absent, leaving consumers without consistent protection or information.

What emerges from this comprehensive synthesis is a picture of a contamination problem that is real and pervasive but still scientifically unfinished. The evidence indicates widespread contamination of bottled water with micro- and nanoplastics, with PET packaging and bottling processes as the dominant sources, and with bottled water consumers likely ingesting more particles than tap water consumers. At the same time, the lack of standardized analytical protocols, the scarcity of certified reference materials, and the incomplete state of knowledge about chronic human health effects together represent a significant challenge for accurate exposure assessment and risk evaluation. For consumers, the findings do not yet translate into clear guidance, but they do puncture the perception of bottled water as a pristine product. For scientists, the priorities are clear: standardize methods, extend detection down to the nanoscale, and generate the toxicological and epidemiological data needed to determine what a lifetime of drinking plastic-laced water actually means for human health.

Subject of Research: Micro- and nanoplastic contamination of bottled water, its sources, detection, health effects, and regulation

Article Title: Microplastic and nanoplastic contamination in bottled water

Article References: Microplastic and nanoplastic contamination in bottled water. (n.d.). https://doi.org/10.1007/s11356-026-38273-y

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38273-y

Keywords: microplastics, nanoplastics, bottled water, PET, drinking water, human health, Raman spectroscopy, FTIR, oxidative stress, water regulation, plastic pollution, exposure assessment