1. IntroductionSince human beings started to colonise the world, slowly migrat-ing (in multiple directions) from the African Rift and ultimatelyreaching the southernmost territories of the Americas, they haveinteracted with the natural environment, using its resources and suf-fering from its hazardous processes. Survival of mankind was possiblethanks to its ability to adapt to an ever-changing environment and itscapability to learn and communicate the new findings. From the ear-liest times, geomorphic features and processes were an essential partof social survival (Crozier et al., 2011). In karst terrains, caves wereused as shelters as well as burial and sacred places, playing an instru-mental role in the day-to-day struggle for survival, especially duringthe ice ages (Fig. 1). Spectacular karst landmarks, such as big cave en-trances, blue karst springs, deep collapse sinkholes (cenotes) or rockarches, just to name a few, have often become part of the naturaland “supernatural” heritage of our ancestors.In prehistoric times the human impact on the karst environmentwas very limited, like the probability of properties and people beingdamaged by karst processes (e.g. subsidence, flooding). Both impactsandhazardsinkarstterrainshaveincreaseddramaticallyover thelasttwo centuries, along with the exponential increase in population andour capability to modify the natural environment, largely related tothe economic and technological development of the societies. An in-creasing number of scientists consider that humans are nowadaysthe most effective geomorphic agent and a prime factor in landscapeevolution (Zalasiewicz et al., 2010; Price et al., 2011). In fact, the for-mal definition of the Anthropocene, as a new epoch of the GeologicalTime Scale characterised by a significant and global human impact onthe Earth's ecosystems, is being debated. At the present time, around25% of the Earth's population lives on or nearby karst areas (Ford andWilliams, 2007) and the increasing exploitation of karst resources,such as water and building material, is leading to severe environmen-tal impacts and unsustainable situations (Drew and Hotzl, 1999;Gunn, 2004). Unfortunately, the number of karst areas affected bywater pollution, landscape degradation and other impacts is growingveryrapidly.Additionally, thedamagecausedbyhazardouskarstpro-cesses, especially subsidence sinkholes (Beck, 2003; Waltham et al.,2005; Gutierrez et al., 2008a), will most likely keep on increasing.Exposed human elements augment and anthropogenic changes inthe karst systems frequently result in hazard enhancement. Karstgeomorphologists and hydrologists can play a decisive role in pre-venting natural disasters in karst areas, particularly those inducedby human activities; dams with leakage and sinkhole problems(Milanovic, 2000; Cooper and Gutierrez, 2011), mines and tunnelsaffected by flooding and subsidence (Li and Zhou, 1999; Autin,2002;Casagrandeet al.,2005;Luchaetal.,2008),high-speedrailwaysbuilt in sinkhole-prone areas (Guerrero et al., 2008) or developmentof sinkholes at huge rates induced by lake level (Yechieli et al.,2006) or water table (Sprynskyy et al., 2009) declines.The importance of properly managing karst areas and mitigatingthe detrimental effects caused by human activities on these inherentlysensitive environments has been boosted by a series of conferencesand projects since the early 1990s (Ford, 1993; Williams, 1993; Pariseet al., 2008; 2009). Raising public awareness on the need to protectour endangered natural resources, especially in developed countries,has promoted the production of karst-specific Environmental ImpactAssessments(Veni,1999).Recently,severalapproacheshavebeenpro-posedtoassessthedegreeofhuman-induceddisturbanceinkarstareas(Van Beynen and Townsend, 2005; Calo and Parise, 2006; De Waele,2009; North et al., 2009). Although these studies are essential for apropermanagementofthekarstresources,theymaybefutileifnotfol-lowed by adequate administrative decisions and regulations.2. Karst geomorphology2.1. Karst processesKarst is characterised by the predominance of rock dissolution overmechanical erosion, and is typical of present temperate (cold andwarm) and tropical environments (Ford and Williams, 2007). In karstterrains, surface and subsurface geomorphology and hydrology arelargely governed by dissolution of carbonate and/or evaporite rocks.In the most classical (common) situation, surface waters, acidified byCO