Long-term Negative Trend Research Articles

Political and socio-economic development of modern Russia: environmental obstacles and risks

The article deals with environmental obstructions and limitations for a dynamic political and socioeconomic development of modern Russia. Environmental problems accumulated in the past decades, including problems that appeared in the "Soviet" period of the country's development, together with growing new environmental risks, become a serious obstacle to the progressive development of the country. Contemporary Russian manufacturing practices continue to use extensively anti-environmental obsolete technologies, which lead to increasing degradation of the natural environment and an increase in negative trends in the health of the population. The absence or limited use of remediation activities in extractive industries has led to the natural degradation of a number of territories in the country. Unfavorable socio-demographic characteristics of the development for modern Russia caused by the environmental factors hinder innovative development in all spheres of society in the present period; moreover, their increasing impact will be an obstacle to socio-economic development in the future. Additionally the article discusses long-term negative trends in the development of environmental policy and weakening of the ecological spectrum of civil society.

Historical trends in spring ice breakup for the Aura River in Southwest Finland, AD 1749–2018

Ice breakup (IBU) observations have been recorded for Aura River in Turku, southwest Finland, since the mid-18th century. The latest long-term investigation covered the period 1749–1906, but the series contains several biases. In this article, we present a fully revised and extended IBU series (1749–2018) of Aura River for climate research purposes. Instead of typical univariate IBU data (a single time series with one data point per year), this series includes three different types of IBU data. These are the initial observations of the ice starting to break up (IBU1), the river recorded as free from ice within city limits (IBU2) and, finally, the arrival of the ice from behind the Halinen dam, the so-called Halinen ice (IBU3). The IBU1 series shows negative, statistically significant long-term trends since 1749. While the other two phenological events also exhibit negative long-term trends, indicative of earlier and warmer springs towards the present day, their trends are not significant over multi-centurial scales. The IBU2 series is the only series covering the entire period, and it shows a significant negative trend towards earlier breakups (16 days) between 1919 and 2018. Consequently, breakups in March, which were extremely rare before the 1900s, have become common, while breakups in May (previously once per decade) have not occurred since 1881. These results are indicative of sub-seasonal trends in the breakups. Our results also confirm defects in the previous time series, which shows a bias of up to 16 days.

Interannual Variability and Seasonality of Precipitation in the Indus River Basin

AbstractThe Indus River basin is highly vulnerable to water scarcity due to increasing population, unsustainable management practices, and climate change. Yet the regional hydroclimate and precipitation dynamics remain poorly understood. Using running trend and spectral analysis with multiple gauge-based, remote sensing, and reanalysis precipitation datasets, this study analyzes precipitation temporal variability, its subregional variations, and the main seasonal drivers, particularly the South Asian monsoon. The results uncover remarkable alternation of long-term positive and negative interdecadal precipitation trends in the basin over the past half century. These trends have led to substantial changes in water input over the region at the time scales comparable to climate assessment periods (30 years), and therefore this high intrinsic variability must be accounted for in climate change adaptation studies. This study also reconstructs onset and withdrawal dates of the South Asian monsoon that exhibit interdecadal variability, but their dominant modes differ from that of annual precipitation. The findings hypothesize that higher-frequency variability in El Niño–Southern Oscillation is likely to have a pronounced impact on monsoon onset and duration in the studied region.

Analysis of actinometric measurements under all-sky and cloud-free conditions in Cáceres (Spain) for the period 1913–1920

Early daily actinometric and cloud cover data from Cáceres (SW of Spain) were recovered for the period 1913–1920. The task of retrieving and digitising early actinometric data series turn out highly required due to the lack of solar radiation data throughout the first half of twentieth century. Firstly, the Arago actinometer and the procedure employed to record the actinometric data were described in detail. Additionally, in spite of being a short series, trends from recovered actinometric data were analysed. A negative trend of (−0.16 ± 0.03) °C/year was obtained for all-sky conditions, reaching a marked value of (−0.26 ± 0.04) °C/year when cloud-free days were selected in the analysis. Both trends were statistically significant at the 95% confidence level. The Katmai eruption in June 1912 likely caused anomalous low actinometric records in 1913 and 1914. These results suggest a decrease of solar radiation in Cáceres during the second decade of the twentieth century which is in accordance with the final stage of the long-term negative trend in solar radiation data observed at several European sites from late nineteenth century to the beginning of the twentieth century (‘early dimming’).

Depopulacija Srbije - borba za opstanak jednog naroda

Demographic indicators in Serbia show a long-term negative trend comparing to global demographic trends. Socioeconomic factors significantly influence demographic trends. Causes of mortality also represent an area that needs to be systematically and urgently regulated as a large number of citizens die of chronic non-communicable diseases. Economic migration cannot be prevented without adequate social and economic policies. The disappearance of Serbs from this territory is forecast for 2225 if such a trend continues. Rural areas are devastated while migration to cities is present. The solution is in economic development, adequate public health and the formation of the Funds for Demographic Development.

An Assessment of Stratospheric Intrusions in Italian Mountain Regions Using STEFLUX

The Mediterranean basin is considered a global hot-spot region for climate change and air quality, especially concerning summer-time ozone (O3). Previous investigations indicated that the Mediterranean basin is a preferred region for stratosphere-to-troposphere exchange (STE) and deep stratospheric intrusion (SI) events. The Lagrangian tool STEFLUX, based on a STE climatology that uses the ERA Interim data, was hereby used to diagnose the occurrence of deep SI events in four mountain regions over the Italian peninsula, spanning from the Alpine region to the southern Apennines. By using near-surface O3 and relative humidity (RH) observations at three high-mountain observatories, we investigated the performance of STEFLUX in detecting deep SI events. Both experimental and STEFLUX detections agreed in describing the seasonal cycle of SI occurrence. Moreover, STEFLUX showed skills in detecting “long-lasting” SI events, especially in the Alps and in the northern Apennines. By using STEFLUX, we found positive tendencies in the SI occurrence during 1979–2017. However, in contrast to similar studies carried out in the Alpine region, the negative long-term (1996–2016) trend of O3 in the northern Apennines did not appear to be related to the SI’s variability.

Least Tern (Sternula antillarum) Population Response to Water Levels on Cheyenne River and Oahe Reservoir, South Dakota, USA

Consideration of annual population count data, stream flows, water levels, and nesting habitat availability over a 29-year period suggest that Least Terns (Sternula antillarum athalossos) nesting along the Cheyenne River and Oahe Reservoir in South Dakota, USA, select areas primarily in response to reservoir water levels early in the breeding season. Generalized linear models were selected in an information-theoretic framework and showed important relationships between adult Least Tern numbers and reservoir levels, as well as a negative long-term temporal trend in both survey areas. Reservoir levels alone could not account for the temporal trend. The number of adult Least Terns on the Cheyenne River was positively correlated (R = 0.668) with mean May reservoir water levels—a more important relationship than that between adult numbers and river levels. The number of adults on the Oahe Reservoir was negatively correlated (R = -0.573) with mean May reservoir water levels. Numbers of adults on the Cheyenne River and on Oahe Reservoir were negatively correlated (R = -0.684), suggesting that birds may interact as one population across the two areas. This information should help managers to consider ecological relationships among segments of the Least Tern population on the Missouri River and its tributaries and options for managing Least Terns on the Cheyenne River, Oahe Reservoir, and elsewhere on the Missouri River system.

ЕКОНОМІКО-МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ АГРАРНОГО СЕКТОРУ ЕКОНОМІКИ УКРАЇНИ

The article analyzes all stages of production of both raw materials and finished agricultural products common for the modern agricultural production in Ukraine. Both the external and internal factors influencing the primary and secondary production of agricultural products were studied. The markets for agricultural raw materials and finished products, namely, the national and international markets for agricultural products, were also considered. Based on the results of analysis, the economic-mathematical model of production and processing of agricultural products as a single economic system has been constructed . The model was built taking into account the most vital requirements of each of the selected stages,. Each of the five stages of production, that were distinguished, was described using mathematical formulas. For some of the steps, the Cobb-Douglas multiplicative production function, modernized for the specifics of agricultural production, was used. The function used includes the influence of the areal factor on the gross agricultural production, as well as classic labor and capital factors. The problem of increasing the efficiency of the agricultural sector of Ukraine's economy was formulated and solved Using this economic-mathematical model of production in the development of agricultural policy and macroeconomic planning will allow to consider changes in the economy of the agricultural and processing industry, to assess the possible consequences of new activities in state economic policy, implementation and monitoring of the long-term negative and positive trends of production and processing of agricultural products. Moreover, due to this model, it could be possible to increase the volume of earnings inforeign currency, which, in turn, can be used as investment not only in agricultural but also in other sectors of the national economy.

Warming is Driving Decreases in Snow Fractions While Runoff Efficiency Remains Mostly Unchanged in Snow-Covered Areas of the Western United States

Abstract Winter snowfall and accumulation is an important component of the surface water supply in the western United States. In these areas, increasing winter temperatures T associated with global warming can influence the amount of winter precipitation P that falls as snow S. In this study we examine long-term trends in the fraction of winter P that falls as S (Sfrac) for 175 hydrologic units (HUs) in snow-covered areas of the western United States for the period 1951–2014. Because S is a substantial contributor to runoff R across most of the western United States, we also examine long-term trends in water-year runoff efficiency [computed as water-year R/water-year P (Reff)] for the same 175 HUs. In that most S records are short in length, we use model-simulated S and R from a monthly water balance model. Results for Sfrac indicate long-term negative trends for most of the 175 HUs, with negative trends for 139 (~79%) of the HUs being statistically significant at a 95% confidence level (p = 0.05). Additionally, results indicate that the long-term negative trends in Sfrac have been largely driven by increases in T. In contrast, time series of Reff for the 175 HUs indicate a mix of positive and negative long-term trends, with few trends being statistically significant (at p = 0.05). Although there has been a notable shift in the timing of R to earlier in the year for most HUs, there have not been substantial decreases in water-year R for the 175 HUs.

Mortality from cardiovascular diseases and life expectancy in Russia

High premature mortality from cardiovascular disease (CVD) and its long-term negative trends are one of the main reasons for Russia's lag behind the developed countries in life expectancy, especially of its female population. Despite the decline in mortality since 2003, CVD mortality rates at particular ages (30-74 years for males and 30-49 for females) are still higher than in 1970.
 Decomposition of long-term changes in life expectancy in Russia shows a negative contribution of changes in CVD mortality for men (-1.0 years in 1972-2010) and a small positive contribution for women (+0.7 years from 1972 to 2010).
 The mortality structure within the full class of cardiovascular diseases in Russia is significantly different from that observed in the countries with the lowest level of CVD mortality. Ischemic heart disease constitutes more than half of all deaths, and this share, in contrast to Western countries, is tending to rise. Second place belongs to deaths from cerebrovascular diseases, the share of which is declining, but remains significantly higher than in Western countries. The share of deaths from other cardiovascular diseases accounts for about 50% of all CVD mortality in Western countries, while in Russia it is only about 15%, but these are characterized by a very low age at death.
 Regional patterns of CVD mortality in Russia are discussed, as well as the quality of statistics on causes of death and changes in the coding practices in the Russian Federation.

Towards a better understanding of long-term wood-chemistry variations in old-growth forests: A case study on ancient Pinus uncinata trees from the Pyrenees

Dendrochemical studies in old forests are still underdeveloped. Old trees growing in remote high-elevation areas far from direct human influence constitute a promising biological proxy for the long-term reconstructions of environmental changes using tree-rings. Furthermore, centennial-long chronologies of multi-elemental chemistry at inter- and intra-annual resolution are scarce. Here, we use a novel non-destructive method by applying Micro X-ray fluorescence (μXRF) to wood samples of old Pinus uncinata trees from two Pyrenean high-elevation forests growing on acidic and basic soils. To disentangle ontogenetic (changes in tree age and diameter) from environmental influences (e.g., climate warming) we compared element patterns in sapwood (SW) and heartwood (HW) during the pre-industrial (1700–1849) and industrial (1850–2008) periods. We quantified tree-ring growth, wood density and relative element concentrations at annual (TRW, tree-ring) to seasonal resolution (EW, earlywood; LW, latewood) and related them to climate variables (temperature and precipitation) and volcanic eruptions in the 18th and 19th centuries. We detected differences for most studied elements between SW and HW along the stem and also between EW and LW within rings. Long-term positive and negative trends were observed for Ca and K, respectively. Cl, P and S showed positive trends during the industrial period. However, differences between sites were also notable. Higher values of Mg, Al, Si and the Ca/Mn ratio were observed at the site with acidic soil. Growing-season temperatures were positively related to growth, maximum wood density and to the concentration of most elements. Peaks in S, Fe, Cl, Zn and Ca were linked to major volcanic eruptions (e.g., Tambora in 1815). Our results reveal the potential of long-term wood-chemistry studies based on the μXRF non-destructive technique to reconstruct environmental changes.

Self-organizing map network-based precipitation regionalization for the Tibetan Plateau and regional precipitation variability

A precipitation-based regionalization for the Tibetan Plateau (TP) was investigated for regional precipitation trend analysis and frequency analysis using data from 1113 grid points covering the period 1900–2014. The results utilizing self-organizing map (SOM) network suggest that four clusters of precipitation coherent zones can be identified, including the southwestern edge, the southern edge, the southeastern region, and the north central region. Regionalization results of the SOM network satisfactorily represent the influences of the atmospheric circulation systems such as the East Asian summer monsoon, the south Asian summer monsoon, and the mid-latitude westerlies. Regionalization results also well display the direct impacts of physical geographical features of the TP such as orography, topography, and land-sea distribution. Regional-scale annual precipitation trend as well as regional differences of annual and seasonal total precipitation were investigated by precipitation index such as precipitation concentration index (PCI) and Standardized Anomaly Index (SAI). Results demonstrate significant negative long-term linear trends in southeastern TP and the north central part of the TP, indicating arid and semi-arid regions in the TP are getting drier. The empirical mode decomposition (EMD) method shows an evolution of the main cycle with 4 and 12 months for all the representative grids of four sub-regions. The cross-wavelet analysis suggests that predominant and effective period of Indian Ocean Dipole (IOD) on monthly precipitation is around ∼12 months, except for the representative grid of the northwestern region.

Reconstructed and Projected U.S. Residential Natural Gas Consumption during 1896–2043

AbstractUsing state-level monthly heating degree-day data, reconstructed per capita natural gas (NGr) consumption records for each state of the continental United States were calculated for 1895–2014 using linear regressions. The regressed monthly NGr values estimate the effects of twentieth- and early twenty-first-century climate variation on per capita natural gas usage, assuming a modern (1990–2013) consumption environment. Using these extended consumption records, the hypothetical effects of climate on past, current, and future natural gas (NG) use are estimated. By controlling for nonclimatic consumption effects, these extended reconstructions provide estimates of the sensitivity of NG consumption to historical climate variation, particularly long-term warming trends, occurring before the period of available consumption records. After detrending, the reconstructions are used to form improved estimates of interannual NG variation under current climate conditions. Given estimates of each state’s current consumption climatology and long-term trends in per capita consumption and current population trends, the net effect of warming and increasing population on future consumption is estimated. Significant long-term negative trends in per capita NG consumption are found in western and northeastern states and in Florida, while southeastern consumption effects reflect a multidecadal temperature cycle. Climate-related consumption effects found here are generally consistent with previous studies, with long-term trend effects limited to less than 12% and multidecadal regime effects limited to less than 9%. Given the stronger positive effects of increasing population on total state natural gas consumption, reduced per capita use associated with warming trends has a weak moderating effect on estimates of projected total consumption in 2043.

Roles of ozone depleting substances and solar activity in observed long-term trends in total ozone column over Indian region

ABSTRACTAn additive time-series decomposition analysis was performed on the Multi Sensor Reanalysis-2 (MSR-2) monthly mean total ozone column (TOC) time-series dataset spanning over 34 years (January 1979–December 2012) for Indian region (0.0–40.0 °N; 67.5–97.5° E). Statistically significant (p-value <0.05) long-term trends in TOC were estimated in the deseasonalized TOC time series. The role of multiple natural and anthropogenic factors: quasi biennial oscillations (QBO), El-Nino Southern Oscillations (ENSO), cyclic variation in solar activity (SA), and ozone depleting substances (ODS) was investigated to explain the long-term trends in TOC over Indian region. Over sub-tropical Indian region (25.0° N– 40.0° N), declining long-term linear trends were estimated, which varied from −0.30% to −1.10% per decade. Interestingly a positive long-term linear-trend (0.10–0.30% per decade) was observed over equatorial-tropical part of Indian region. No statistically significant long-term trend was observed for 30mb Equatorial Zonal Winds and Nino 3.4 index – indicators for QBO and ENSO; however, a positive long-term linear trend of magnitude 17.00 ± 1.18% per decade was observed in effective equivalent stratospheric chlorine – a proxy for ODS, and a negative long-term linear trend of magnitude 12.72 ± 2.86% per decade was observed in 10.7 cm Solar Radio Flux – a representative for SF. It is inferred that over the Indian region above tropic of cancer, about 85.00% of the estimated negative long-term linear trend in TOC can be explained by the increase in the stratospheric concentration of ODS; whereas, decrease in the solar activity accounted for 15.00% of the estimated negative long-term linear trend in TOC over sub-tropical Indian region.

Multidecadal Trends and Interannual Variability of Rainfall as Observed from Five Lowland Stations at Mt. Kilimanjaro, Tanzania

Abstract Future rainfall dynamics in the Kilimanjaro region will mainly be influenced by both global climate and local land-cover change. An increase in rainfall is expected, but rising temperatures are also predicted for the ecosystem. In situ rainfall of five stations is analyzed to determine seasonal variability and multidecadal trends in the lowlands and lower elevations of the Kilimanjaro region. Monthly rainfall totals are obtained from the Tanzanian Meteorological Agency, from two mission stations, and from a sugar cane plantation. The datasets of the two mission stations cover time spans of 64 and 62 years, starting in 1940 and 1942, while rainfall data obtained from the Tanzanian Meteorological Agency and from the sugar cane plantation start in 1973 and 1974 and thus cover 40–41 years. In one out of five stations, a significant weak negative linear long-term trend in rainfall is observable, which is also evident in the other locations but is not significant. However, humid and dry decades are evident and seasonality has changed, especially during the long rains between March and May. El Niño–Southern Oscillation (ENSO) in combination with positive Indian Ocean dipole (IOD) leads to enhanced rainfall during the year of ENSO onset and the following year. During La Niña years, rainfall increases in the following year, while during the onset year rainfall patterns are more diverse. Positive IOD leads to enhanced rainfall amounts.

Environmental and Anthropogenic Degradation of Vegetation in the Sahel from 1982 to 2006

There is a great deal of debate on the extent, causes, and even the reality of land degradation in the Sahel. Investigations carried out before approximately 2000 using remote sensing data suggest widespread reductions in biological productivity, while studies extending beyond 2000 consistently reveal a net increase in vegetation production, strongly related to the recovery of rainfall following the extreme droughts of the 1970s and 1980s, and thus challenging the notion of widespread, long-term, subcontinental-scale degradation. Yet, the spatial variations in the rates of vegetation recovery are not fully explained by rainfall trends. It is hypothesized that, in addition to rainfall, other meteorological variables and human land use have contributed to vegetation dynamics. Throughout most of the Sahel, the interannual variability in growing season ΣNDVIgs (measured from satellites, used as a proxy of vegetation productivity) was strongly related to rainfall, humidity, and temperature (mean r2 = 0.67), but with rainfall alone was weaker (mean r2 = 0.41). The mean and upper 95th quantile (UQ) rates of change in ΣNDVIgs in response to climate were used to predict potential ΣNDVIgs—that is, the ΣNDVIgs expected in response to climate variability alone, excluding any anthropogenic effects. The differences between predicted and observed ΣNDVIgs were regressed against time to detect any long-term (positive or negative) trends in vegetation productivity. Over most of the Sahel, the trends did not significantly depart from what is expected from the trends in meteorological variables. However, substantial and spatially contiguous areas (~8% of the total area of the Sahel) were characterized by negative, and, in some areas, positive trends. To explore whether the negative trends were human-induced, they were compared with the available data of population density, land use, and land biophysical properties that are known to affect the susceptibility of land to degradation. The spatial variations in the trends of the residuals were partly related to soils and tree cover, but also to several anthropogenic pressures.

Volunteer Conservation Action Data Reveals Large-Scale and Long-Term Negative Population Trends of a Widespread Amphibian, the Common Toad (Bufo bufo).

Rare and threatened species are the most frequent focus of conservation science and action. With the ongoing shift from single-species conservation towards the preservation of ecosystem services, there is a greater need to understand abundance trends of common species because declines in common species can disproportionately impact ecosystems function. We used volunteer-collected data in two European countries, the United Kingdom (UK) and Switzerland, since the 1970s to assess national and regional trends for one of Europe’s most abundant amphibian species, the common toad (Bufo bufo). Millions of toads were moved by volunteers across roads during this period in an effort to protect them from road traffic. For Switzerland, we additionally estimated trends for the common frog (Rana temporaria), a similarly widespread and common amphibian species. We used state-space models to account for variability in detection and effort and included only populations with at least 5 years of data; 153 populations for the UK and 141 for Switzerland. Common toads declined continuously in each decade in both countries since the 1980s. Given the declines, this common species almost qualifies for International Union for the Conservation of Nature (IUCN) red-listing over this period despite volunteer conservation efforts. Reasons for the declines and wider impacts remain unknown. By contrast, common frog populations were stable or increasing in Switzerland, although there was evidence of declines after 2003. “Toads on Roads” schemes are vital citizen conservation action projects, and the data from such projects can be used for large scale trend estimations of widespread amphibians. We highlight the need for increased research into the status of common amphibian species in addition to conservation efforts focusing on rare and threatened species.

Where does the water go? Understanding geohydrological behaviour of Andean catchments in south-central Chile

ABSTRACTUpper Diguillín and Renegado are two neighbouring Andean basins of south-central Chile, with different specific discharges that cannot be explained solely by their difference in size. To address this issue, this study considers three separate but complementary approaches: (a) long-term analysis of rainfall and flow trends; (b) determination of hydrogeological properties at the watershed scale; and (c) analysis of the temporal evolution of groundwater storage. First, a trend test detected a statistically significant discharge decrease for Renegado in summer, unrelated to a coincidental precipitation trend, which seems to be associated with an increased use of water in that season related to tourism activity in the area. Second, there were no important differences in hydraulic conductivity or drainable porosity between the two study areas. However, it was found that there is a long-term negative trend in groundwater storage for Renegado; that is, water that contributes to the lower Diguillín streamflow through numerous springs.Editor Z. W. Kundzewicz Associate editor not assigned

Combined Assessment of Climate Change and Socio-Economic Development as Drivers of Freshwater Availability in the South of Portugal

A combined assessment of the potential impacts from climate change (CC) and socio-economic development (SED) on water resources is presented for the most important aquifer in the south of Portugal. The goal is to understand how CC and SED affect the currently large pressures from water consuming and contaminating activities, predominantly agriculture. Short-term (2020–2050) and long-term (2070–2100) CC scenarios were developed and used to build aquifer recharge and crop water demand scenarios, using different methods to account for uncertainty. SED scenarios were developed using bottom-up and top-down methods, and discussed at workshops with farmers and institutional stakeholders in the water sector. Groundwater use was quantified for each scenario. Together with the recharge scenarios, these were run through a calibrated groundwater flow model, to study their individual and joint impacts on groundwater levels and discharge rates into a coastal estuary. Recharge scenarios show clear negative long-term trends and short-term increase in temporal variability of recharge, though short-term model uncertainties are higher. SED scenario 1 (SED1), predicting intensification and decline of small farms, considered the most likely by all workshop participants, shows a large drop in agricultural area and water demand. SED2, a most desired scenario by farmers, foresees growth and modernization of agriculture, but proves unsustainable in combination with predicted CC without efficient adaptation measures. The results thus reveal that CC in the region will dynamically interact with economic factors, and going one step beyond, CC could be directly integrated as a constraint in the development of SED scenarios. Exercises involving the integration of CC and SED regionally based scenarios, constructed in both bottom-up and top- down fashion and discussed in participatory contexts are still rarely used for adaptation, and specifically adaptation of agriculture to water scarcity. The joint analysis of CC and SED revealed challenging, as it involved the use of different methods across the border between natural and social sciences. In our view this method contributes in an encouraging manner to a more holistic and transdisciplinary water management, by allowing a more plausible identification of what (and if) adaptation measures are needed.

Long-term citizen-collected data reveal geographical patterns and temporal trends in lake water clarity.

We compiled a lake-water clarity database using publically available, citizen volunteer observations made between 1938 and 2012 across eight states in the Upper Midwest, USA. Our objectives were to determine (1) whether temporal trends in lake-water clarity existed across this large geographic area and (2) whether trends were related to the lake-specific characteristics of latitude, lake size, or time period the lake was monitored. Our database consisted of >140,000 individual Secchi observations from 3,251 lakes that we summarized per lake-year, resulting in 21,020 summer averages. Using Bayesian hierarchical modeling, we found approximately a 1% per year increase in water clarity (quantified as Secchi depth) for the entire population of lakes. On an individual lake basis, 7% of lakes showed increased water clarity and 4% showed decreased clarity. Trend direction and strength were related to latitude and median sample date. Lakes in the southern part of our study-region had lower average annual summer water clarity, more negative long-term trends, and greater inter-annual variability in water clarity compared to northern lakes. Increasing trends were strongest for lakes with median sample dates earlier in the period of record (1938–2012). Our ability to identify specific mechanisms for these trends is currently hampered by the lack of a large, multi-thematic database of variables that drive water clarity (e.g., climate, land use/cover). Our results demonstrate, however, that citizen science can provide the critical monitoring data needed to address environmental questions at large spatial and long temporal scales. Collaborations among citizens, research scientists, and government agencies may be important for developing the data sources and analytical tools necessary to move toward an understanding of the factors influencing macro-scale patterns such as those shown here for lake water clarity.