**7. Discussion on the global significance of environmental alterations in lakes catchments**

The people and their societies are integrated parts of the biosphere. They are dependent on its function and support, but at the same time they are shaping the biosphere globally with marked geological consequences (Steffen et al., 2011). This issue is much broader than the climate change *per se* (Folke et al., 2011). A key challenge for humanity in this new situation is to understand its role in the 'Earth System', start accounting for and governing natural capital and actively shape development in tune with the biosphere (Jansson et al., 1994; Rockström et al., 2009).

It is usually emphasised that during the last couple of generations we have witnessed an amazing expansion of human activities into a converging globalised society, enhancing the material standard of living for a large proportion of people on Earth (Rosling, 2010). This expansion has been quite pronounced since the 1950s, which predominantly benefitted the industrialised world, has pushed humanity into a new geological era, the *Anthropocene*, and

Environmental Changes in Lakes Catchments

Lake system.

by foresters).

**8. Conclusions** 

as a Trigger for Rapid Eutrophication – A Prespa Lake Case Study 115

Fig. 40) have been confirmed many times over in the recent past, but this is the first time they have been detected one millennium ago (Fig. 35). The change from the N driven system towards the P dominated one can only be attributed to intensive P leaching and washout of the karst based geology repeatedly deprived of significant vegetation cover. Human activities in the last 500 years have only added to the already initiated change of the Prespa

Strategies for development that ignore the dynamics of the broader social–ecological system may push people into vulnerable situations and persistent traps, and undermine the capacity to sustain human wellbeing in the long-term. Science has responsibility to provide a better understanding of the challenges facing humanity and to explore pathways toward a sustainable world. Global and regional scale integrated assessments, inclusive, transparent, and founded on an understanding of social–ecological interactions play a central role in

Fig. 40. Clear forest cuts on Bigla Mountain, Prespa Lake watershed (contemporary practice

The surface waters of Prespa Lake watershed are found to be under intensive human pressure. This pressure is expressed through various physical impacts like alterations of the water courses and water abstraction, chemical pollution originating from untreated wastewaters or agriculture, and deterioration of natural biodiversity by introduction of alien species or over fishing. The intensity and duration of the negative human impacts on Prespa

building momentum for 'Planetary Stewardship' (Folke et al., 2011).

generated the bulk of the global environmental changes with potential thresholds and tipping points, currently challenging the future wellbeing of the human population on Earth (Steffen et al., 2007).


Table 10. Reference conditions for Prespa Lake.

The work presented in this chapter enabled a slightly different point of view which broadens the scope of human alterations of nature significantly beyond the last few generations. Namely, if a prolonged civilisation was present in a certain area, like Lake Prespa in our case, in which the geological conditions are fragile enough to critically influence the recipient waters (the lake in our case), than the anthropogenic history of impact is traceable. Unlike soils, water ecosystems can and will accumulate excess chemical compounds very rapidly, but will also rapidly release them in a given situation. This increasing of the 'total capacity' (Svirčev et al., 2010) of a water ecosystem inevitably alters the natural environmental balance and forces the accelerated eutrophication or the rapid aging of the ecosystem. In the case of Prespa Lake, the total deforestations (or the clear cuts –

generated the bulk of the global environmental changes with potential thresholds and tipping points, currently challenging the future wellbeing of the human population on Earth

*Reference conditions for Prespa Lake* 

*Parameter (units)* Value

*pH* 7-8 *NHx-N ( mg\*L-1)* <0.05 *NOx-N ( mg\*L-1)* <1.0 *Total N ( mg\*L-1)* <3.0 *PO4-P ( mg\*L-1)* <0.005 *Total P ( mg\*L-1)* 0.015-0.025

*Secchi depth (m)* >5

*Dissolved oxygen ( mg\*L-1)* 6-7 (surface); >4 (bottom)

*S\*cm-1)* 200-300

*g\*L-1)* <3.8

*Dominant algae* Diatoms, Chrysophytes, Green coccoid algae,

group. *Dominant benthic invertebrates* Snails, Clamps, Dragon flies, Mayflies, Caddis

The work presented in this chapter enabled a slightly different point of view which broadens the scope of human alterations of nature significantly beyond the last few generations. Namely, if a prolonged civilisation was present in a certain area, like Lake Prespa in our case, in which the geological conditions are fragile enough to critically influence the recipient waters (the lake in our case), than the anthropogenic history of impact is traceable. Unlike soils, water ecosystems can and will accumulate excess chemical compounds very rapidly, but will also rapidly release them in a given situation. This increasing of the 'total capacity' (Svirčev et al., 2010) of a water ecosystem inevitably alters the natural environmental balance and forces the accelerated eutrophication or the rapid aging of the ecosystem. In the case of Prespa Lake, the total deforestations (or the clear cuts –

Xanthophytes, Charophytes.

eutrophic conditions

No cyanobacteria or 'water blooms' by any algal

flies, Leeches, Sponge, Amphipods, Decapods. No Chironomids or Tubificids indicators for

> >3 2.33-3.00

(Steffen et al., 2007).

*Conductivity (*

*Chlorophyll* **a** *(*

**BQI index** 

**Diversity index H** 

Table 10. Reference conditions for Prespa Lake.

μ

μ

Fig. 40) have been confirmed many times over in the recent past, but this is the first time they have been detected one millennium ago (Fig. 35). The change from the N driven system towards the P dominated one can only be attributed to intensive P leaching and washout of the karst based geology repeatedly deprived of significant vegetation cover. Human activities in the last 500 years have only added to the already initiated change of the Prespa Lake system.

Strategies for development that ignore the dynamics of the broader social–ecological system may push people into vulnerable situations and persistent traps, and undermine the capacity to sustain human wellbeing in the long-term. Science has responsibility to provide a better understanding of the challenges facing humanity and to explore pathways toward a sustainable world. Global and regional scale integrated assessments, inclusive, transparent, and founded on an understanding of social–ecological interactions play a central role in building momentum for 'Planetary Stewardship' (Folke et al., 2011).

Fig. 40. Clear forest cuts on Bigla Mountain, Prespa Lake watershed (contemporary practice by foresters).
