126 Elena Fernández-Miranda Cagigal
provides the plant with an extra feature. Due to the promising role on
ecological reforestation of the DSE, further research is needed, including
new approaches (molecular, histological and physiological) that will
allow to better characterize the relationship between these fungi and
plants growing in polluted areas.INTRODUCTION
Soil is one of the most sensitive and vulnerable natural resources to
pollution and degradation. According to the Global Soil Partnership (GSP), an
organism belonging to the Food and Agriculture Organization of the United
Nations (FAO), soil is defined as a finite natural resource, non-renewable, as
well as a fundamental basis for agricultural and sustainable development. Soil
provides the foundation for food, fuel, fibre, water availability, nutrient
cycling, organic carbon stocks and biodiversity. The surface of fertile soil is
limited and is increasingly under pressure due to climate change and
competing, unsuitable land uses, resulting in increasing degradation, so much
so that currently 46% of the world’s lands are considered degraded (GSP,
2011).
Industrial activity, mining, intensive farming systems and infrastructures
generate emissions and pollutant discharges in soil produce that are among,
heavy metals the most dangerous elements derived from such activities,
causing serious problems in many areas around the world (Gadd, 2007) due
the quality reduction of the physical and chemical properties of the soil (Simon
et al., 2000).
The European Environment Agency (EEA, 1999) defines heavy metals as
stable metal or metalloid materials with a density greater than 4.5 g/cm^3.
According to the report of the Effects Coordination Center (Posch et al.,
2005), the distribution and magnitude of the deposition of these elements
constitute a serious risk to large areas of European ecosystems. This fact is
reflected in the Geochemical Atlas of Europe (de Vos & Tarvainen, 2006) and
in the results of Lado et al., (2008), which performed a geostatistical study
based on data from the 26 countries that make up the Forum of European
Geological Surveys (FOREGS), demonstrating the high extent of affected land
and clear correlation between high concentrations of cadmium (Cd), cupper
(Cu), mercury (Hg), lead (Pb) and zinc (Zn), and industrial activity and/or
intensive agriculture.