Geological settings of the protected Selisoo mire (northeastern Estonia) threatened by oil shale mining

The protected Selisoo mire in northeastern Estonia is located above valuable oil shale resources, partly in the permitted mining area. We describe in detail the geomorphology and geological setting of the mire to understand the natural preconditions for its formation, development and preservation. We used the LiDAR-based digital elevation model for relief analysis, mapped the peat thickness with ground-penetrating radar and described the Quaternary cover through corings. Ridges, oriented perpendicular to the generally southward-sloping terrain, and shallow depressions at the surface of mineral soil have influenced mire formation and its spatio-temporal dynamics. The Quaternary cover under the mire is thin and highly variable. Therefore the mire is hydro­geologically insufficiently isolated from the limestone bedrock that is drained by the nearby oil shale mine and consequently the mining activities approaching the mire may have a negative influence on the wetland and proposed Natura 2000 site. Natura 2000 type wetlands, both protected or currently outside the nature reserves, cover a significant portion of the prospective oil shale mining areas. The distribution and resilience of those sites may significantly influence further utilization of oil shale resources

On the Use of Unmanned Aerial Systems for Environmental Monitoring

Environmental monitoring plays a central role in diagnosing climate and management impacts on natural and agricultural systems; enhancing the understanding of hydrological processes; optimizing the allocation and distribution of water resources; and assessing, forecasting, and even preventing natural disasters. Nowadays, most monitoring and data collection systems are based upon a combination of ground-based measurements, manned airborne sensors, and satellite observations. These data are utilized in describing both small- and large-scale processes, but have spatiotemporal constraints inherent to each respective collection system. Bridging the unique spatial and temporal divides that limit current monitoring platforms is key to improving our understanding of environmental systems. In this context, Unmanned Aerial Systems (UAS) have considerable potential to radically improve environmental monitoring. UAS-mounted sensors offer an extraordinary opportunity to bridge the existing gap between field observations and traditional air- and space-borne remote sensing, by providing high spatial detail over relatively large areas in a cost-effective way and an entirely new capacity for enhanced temporal retrieval. As well as showcasing recent advances in the field, there is also a need to identify and understand the potential limitations of UAS technology. For these platforms to reach their monitoring potential, a wide spectrum of unresolved issues and application-specific challenges require focused community attention. Indeed, to leverage the full potential of UAS-based approaches, sensing technologies, measurement protocols, postprocessing techniques, retrieval algorithms, and evaluation techniques need to be harmonized. The aim of this paper is to provide an overview of the existing research and applications of UAS in natural and agricultural ecosystem monitoring in order to identify future directions, applications, developments, and challengespublishersversionPeer reviewe

Maalihked Lääne-Eesti savipinnases

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Maalihkeid seostatakse tavaliselt mägiste ning sademeterohkete aladega, kuid ka tasase pinnamoega Eestis toimuvad gravitatsioonist tingitud pinnase liikumised. Esimesed teated maalihetest Eestis ulatuvad mitmesaja aasta taha, kui Vigalasse ehitatud vastne mõisahoone jõkke libises. Eesti kõige maalihkeohtlikum piirkond on Pärnu ümbrus, kus viirsavitasandikku lõikunud jõeorgudes on toimunud ja toimuvad ka tänapäeval küllaltki ulatuslikud nõlvade purunemised. Suurim teadaolev maalihe toimus 1976. aastal Sauga jõe ääres ning liigutas hinnanguliselt ühe korraga 100 000 m3 pinnast. Alates 2002. aastast on Tartu Ülikooli geoloogia osakond uurinud Pärnu ümbruses toimunud maalihete levikut, mehhanismi ning vallandavaid tegureid. Tehtud tööd on kokku võetud käesolevas doktoritöös. Maalihete inventuuri tulemusena on koostatud maalihete andmebaas, mis hetkel sisaldab andmeid 26 maalihke kohta. Maalihete suurimateks koondumiskohtadeks on Eametsa küla Sauga jõe ääres ning Tammiste külas Pärnu jõe ääres. Valdavalt viir¬savist koosnevatel nõlvadel toimuvad mitmest järjestikust lihkest toimuvad lihke¬kompleksid alates 10° nõlvakaldest, tüsedama liivakihi korral toimuvad üksikud pöördlihked alates 20° nõlvakaldest. Tüüpiliselt vallandab lihke põhjaveetaseme (poorirõhkude) tõus, põhiliseks ettevalmistavaks protsessiks on aga jõgeline erosioon. Poorirõhud on kõige muutlikumad viirsavide ülemises osas ning ka poorirõhkudest mõjutatud nõlva püsivus muutub sesoonselt rohkem savinõlvades. Välitöödel ning modelleerimisel kogutud andmestiku põhjal koostati Pärnu ümbruse maalihete ohtlikkuse kaart. Kõige ohtlikumaks osutus valdavalt viirsavist nõlvadega Sauga jõe org. Jõeorgude metsastamine oleks kõige efektiivsem viis maalihete ohu vähendamiseks, sest see pidurdaks erosiooni ning alandaks poorirõhkusid nõlvades.Landslides are one of the most costly natural hazard that human kind has to face. Since 2002 Department of geology from University of Tartu has been investigating landslides in the Pärnu region, the most unstable area in Estonia. Most of the landslides take place on convex slopes of the river valleys, altogether 26 landslides are currently added to the landslide inventory. Landslides form two distinctive groups: larger, retrogressive landslide complexes affecting clayey slopes of the Sauga and Audru River valleys and smaller, single rotational slope failures affecting sandy slopes in the Pärnu and Reiu River valleys. River erosion is the main preparatory process of landslides. Water-related phenomena, like excess pore pressures, seepage, loss of negative pore pressure, etc., are the main triggers for slope failures. Pore pressure fluctuations are mostly controlled by the temperature and related snow-melt and have a strong effect on the stability of clayey slopes whereas the stability of the sandy slopes is less affected. The Sauga River valley is the most unstable region in the study area according to landslide susceptibility mapping. Reforestation and drainage of river banks would decrease river undercutting and stabilize valley slopes most effectively

Performance of a Bog Hydrological System Dynamics Simulation Model in an Ecological Restoration Context: Soomaa Case Study, Estonia

We describe how a bog hydrology simulation model, developed in the System Dynamics environment, predicts the changes in the groundwater levels that result from drainage ditch closure and partial thinning of the surrounding forest stand. Five plots were selected in an area that was subjected to such ecological restoration, and the observed groundwater levels were compared with the simulated ones. Across the plots, the mean difference between the observed and simulated groundwater curves varied between 0.88 and 2.63 cm, and the RMSE between 0.28 and 0.71. Although the absolute difference between the predicted vs. observed values was greater in the plots with ditch closure, the curves co-varied more closely there over time. Therefore, hydrological System Dynamics models can be particularly useful for relative comparisons and risk-mapping of novel management scenarios

Interpreting Estonian mires: common perceptions and changing practices

Over the centuries mires have been considered to be mostly useless, even dangerous places. Adopting a landscape semiotic perspective the article delineates the current common perceptions of Estonian mires based upon 767 questionnaires. Today the mire is commonly perceived as undisturbed wilderness offering possibilities for various recreational as well as traditional activities. The image of mires in popular consciousness is predominantly based on touristic experience of protected areas. The history of the most widespread practices in the mires over the 20th century reveals three general paradigmatic frames of reference: traditional where mire appears to be liminal; industrial where it is encultured; and ecological where mire is aestheticized. In its orientation towards aesthetic and emotional values the common perspective diverges from the landscape ecological definition. Tourism to non-protected, partly meliorated mires should be encouraged to give a more realistic perspective of the mires to non-professionals

Interpreting Estonian mires: common perceptions and changing practices

Over the centuries mires have been considered to be mostly useless, even dangerous places. Adopting a landscape semiotic perspective the article delineates the current common perceptions of Estonian mires based upon 767 questionnaires. Today the mire is commonly perceived as undisturbed wilderness offering possibilities for various recreational as well as traditional activities. The image of mires in popular consciousness is predominantly based on touristic experience of protected areas. The history of the most widespread practices in the mires over the 20th century reveals three general paradigmatic frames of reference: traditional where mire appears to be liminal; industrial where it is encultured; and ecological where mire is aestheticized. In its orientation towards aesthetic and emotional values the common perspective diverges from the landscape ecological definition. Tourism to non-protected, partly meliorated mires should be encouraged to give a more realistic perspective of the mires to non-professionals

CAN Bog Breathing be Measured by Synthetic Aperture Radar Interferometry

Accounting for relatively large seasonal and short term peatland surface vertical displacements with Synthetic Aperture Radar Interferometry (InSAR) poses a problem of possible propagation of ambiguity errors. Notwithstanding, the absence of continuous high temporal resolution peatland surface levelling measurements for validation has been something characteristic. Based on the ground levelling from a raised bog, we demonstrate the Sentinel-1 distributed scatterer (DS) time-series InSAR technique underestimates real surface displacements and hereby we question the accuracy of the approach over peatlands. When the relative surface change from 6-day interferograms is used instead of accounting for the absolute change, the estimation accuracy improves (Spearman's rho 0.82, p-value < 0.002) because 6-day in situ surface changes are usually small and do not need InSAR phase unwrapping. Despite a serious unwrapping problem in peatlands, DS time series contain useful signal and differential InSAR (DInSAR) might have potential for assessment of short term peatland surface displacements in favourable conditions

Reliability of Sentinel-1 InSAR distributed scatterer (DS) time series to estimate the temporal vertical movement of ombrotrophic bog surface

A better understanding of the short term and seasonal peat surface vertical displacements (bog breathing) (Roulet 1991) initiated by changes in the water table is needed to improve spatial models of greenhouse gas emissions (Dise 2009). Synthetic Aperture Radar Interferometry (InSAR) is a promising tool for the task but accounting for relatively large peat surface displacements (Fritz 2006, Howie & Hebda 2018) may cause propagation of ambiguity errors and unreliability (Alshammari et al. 2018, Heuff & Hanssen 2021). This is usually overlooked and the absence of ground levelling data for validation is characteristic of InSAR research in peatlands (Cigna & Sowter 2017, Alshammari et al. 2018). We calculated distributed scatterer (DS) time series over 2014–2020 for Sentinel-1 relative orbits number (RON) 80 (descending) and 160 (ascending). The high frequency continuous in situ ground levelling measurements cover the snow and ice-free period of 2016 (April–October). Limited by the availability of Sentinel-1 data, 13 images from both stacks were evaluated against the levelling of a hummock plot. DS points used in the comparison were located around the plot at 125–315 m. The bog points were referenced to the stable DS points from a nearby village (4 km away) to account for atmospheric effects. InSAR line of sight deformation results were projected to vertical dimension (uLOS). Concerning only the dates when we had SAR acquisitions, the largest change relative to the maximum surface level of the period is -6.6 cm and median change -2.4 cm for RON 80, and -7.5 cm and -2.4 cm for RON 160. The maximum deviation between the uLOS and the levelling is 5.6 cm and median 2.11 cm for RON 80. For RON 160, the maximum deviation is 5.85 cm and median 2.81 cm. The Spearman correlation coefficient (rs) between the uLOS and the levelling is 0.84 for RON 80 and rs = 0.81 for RON 160 (p-value < 0.001 in both cases). To reduce the need for ambiguity resolution in the DS time series, we used relative changes between two consecutive acquisitions (baseline of 12 or 6 days) instead of accounting for the absolute change. The in situ relative surface changes between the consecutive acquisition dates of RON 80 are -2.55...2.1 cm (median -0.08 cm) and the deviation of the DS from the levelling is -1.17...1.28 cm (median 0.38 cm). For RON 160, levelling values are -0.9...3.3 cm (median -0.3 cm) and the deviation -3.06…0.81 cm (the former is -0.45 if the 12-day image pair corresponding to the change larger than the uLOS height of ambiguity is removed), median 0.23 cm. Between the levelling and DS data rs = 0.67 (p-value 0.035) and 0.77 (p-value 0.005), respectively for RON 80 and 160. Based on the in situ levelling, we demonstrated that 1) Sentinel-1 DS time series severely underestimate real surface changes over the bog and 2) despite a serious ambiguity problem, DS time series contain the useful signal because 6-day surface changes are relatively small and usually do not need ambiguity resolution