Browsing by Subject "Population density"

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  • Järvinen, Jaakko (Helsingin yliopisto, 2019)
    The main thesis of economies of agglomeration is that by increasing the density of employment, economic benefits will follow. In this research, this hypothesis is tested in the context of the Nordic countries by studying if the increases in the employment density affect the regional productivity. This effect between the employment density and regional productivity is called the agglomeration effect. The theoretical background of this effect lies in three fundamental concepts: economies of scale, labor pooling and knowledge spillovers. Cities have their origins in the economies of scale and ag- glomerations of people they comprise of form a fertile base for effective matching between employers and employees. The denser these production centers are populated, the easier it is for the spillovers of innovation and ideas to happen. This study uses a linear ordinary least squares (OLS) model to estimate this effect. The data consists of 70 regional observations and the model comprises of employment density as the explanatory variable, varying number of education level control variables and dummy variables for different countries. Endogeneity of the explanatory variable is also assessed but as the proposed instrument, the total land area of the included regions, proves to be invalid for this particular geographic region, the OLS estimates will serve as the final results. In the previous studies conducted in Europe and in the USA, the magnitude of the agglomeration effect has been found to be between 4.4 and 6 %. This study’s estimates tell the effect to be between 2.1 and 2.9 % in the Nordic countries that is lower than the corresponding values for the aforementioned regions. This result is discussed to stem from the unique geographical and political characteristics of the Nordic regions.
  • Rask, Martti; Malinen, Tommi; Olin, Mikko; Nyberg, Kari; Ruuhijarvi, Jukka; Kahilainen, Kimmo K.; Verta, Matti; Vuorenmaa, Jussi; Blauberg, Tarja-Riitta; Arvola, Lauri (2021)
    High dissolved organic carbon and low pH are often associated with elevated mercury content of fish in boreal lakes, but less is known about the fish mercury dynamics in lakes recovering from acidification stress. We measured total mercury concentration (THg) in muscle of European perch (Perca fluviatilis) and evaluated the overall correlation with environmental and growth variables in 24 boreal headwater lakes in the 2010s. We found negative correlations of length-corrected perch THg with lake pH and perch growth, but no correlation with dissolved organic carbon. The main emphasis in the present study was focused to a subset of ten lakes in southern Finland with known perch THg during severe acidification in the 1980-1990s. The comparison of perch THg concentrations in the 2010s with values determined in the 1980-1990s showed a sharp increase in most acidic lakes where the perch populations suffered from severe acid stress in the 1980s. This increase was attributed to growth condensation caused by sharp decrease in perch growth during recovery of reproduction capacity and the consequent increases in population densities of perch. Our results highlight the importance of perch growth rate and population density for understanding the variability of fish Hg in boreal headwater lakes, where recovery from acidification can lead to higher mercury concentration of fish in certain cases.