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2  Degradation in Northern Africa: a multi-causal phenomena

               The timing, rate and direction of climate change is the cumulative result of natural variability, anthropogenic
               forcing and the resultant terrestrial-atmospheric feedbacks. Palaeoclimatological records indicate a strong
               relation between the Earth’s orbital parameters (Milankovitch cycles) and the planetary climate conditions
               (Pausata et al., 2020). Since the beginning of the Pleistocene 2.6 million years ago, there have been over 20
               ice ages driven by orbital changes, which have had significant effects on global climates extending to the
               equatorial regions  (Crucifix, 2012; Herbert et al., 2010). However, climate variations throughout history
               cannot be explained by Milankovitch cycles alone. The general conclusion of long-term ecological research
               shows that shifting regimes are always multi-causal (Foley et al., 2013) and the role of anthropogenic forcing
               in driving continental-scale changes to land cover may have been much more significant than previously
               understood (Boivin et al., 2016; Hoag & Svenning, 2017; Wright, 2017). The profound potential of humans
               to reduce vegetal biomass is not restricted to the post-industrial era, but rather dates back far into prehistory,
               a period some call the Palaeoanthropocene: ‘the time interval before the industrial revolution during which
               anthropogenic effects on landscape and environment can be recognized, but before the burning of fossil
               fuels produced a huge crescendo in anthropogenic effects’ (Foley et al., 2013). This hypothesis further claims
               humans  have  actively  and  interdependently  co-evolved  with  their  landscapes  in  the  form  of  ‘niche
               construction’ in which organisms’ trophic behaviours correspondingly shape the ecosystems they inhabit
               (Braje & Erlandson, 2013; Glikson, 2013; Thompson et al., 2021). Decoupling the interplay of human agency
               in shaping the environment is laden with uncertainty. This all begs the question: What is the ‘natural’ climate
               and what role does humanity play in shaping planetary functioning over longue-durée timescales?

               Socio  hydrological  interactions  in  the  form  of  land-use  change  touch  upon  all  green  water  variables  –
               terrestrial  precipitation,  evaporation  and  soil  moisture.  Land-use  change  alters  precipitation  patterns
               through the modification of the local land–atmosphere coupling and large-scale circulation patterns (Pitman
               et al., 2012; Runyan et al., 2012; Wang-Erlandsson et al., 2018). As for evaporation – agriculture and pasture
               expansions (now covering almost half Earth’s ice-free land area) has estimated effects of 2,000–3,000 km /yr
               decreases  and  800–2,600  km /yr  increases  in  evaporation  –  as  a  result  of  deforestation  and  irrigation,
               respectively  (Gordon  et  al.,  2005).  Soil  moisture  functions  as  the  interface  between  precipitation  and
               evaporation, which implies that changes in soil moisture retention and availability to plants could generate
               non-linear ecological, biogeochemical and atmospheric changes across scales (Wang-Erlandsson et al., 2022).

               In all efforts to restore or regenerate ecosystems we ought to be aware of the root causes and potentially
               amplifying feedbacks that lead the changing of landscapes and the inherit uncertainties therein. In this light,
               although regreening efforts can have desirable effects for climate mitigation and biodiversity, afforestation
               initiatives are still widely criticised. One major criticism that came from global analyses (e.g., Bastin et al.,
               2019) is that those new forests are planned on places which have always supported other ecosystems with
               their own functioning and biodiversity. This criticism emphasizes the necessity of conducting complementary
               historical analyses of changing ecosystems including the dynamics of their functioning and the degree of
               human  agency  in  inducing  regime  shifts.  Moreover,  restoration  action  must  assess  the  feasibility  of
               intentionally inducing ecological regime shifts and the associated (regional and global) impacts of doing so.

               2.1  Palaeoclimatological and geomorphological signs of degradation

               Degradation is defined in this report as the negative trend in land condition, including the loss of at least one
               of the following: biological productivity, ecological integrity, or value to humans (Olsson et al., 2019). Like
               many  other  deserts  on  Earth,  the  Sahara  (which  in  biofunctionality  includes  the  Sinai  Peninsula)  have
               witnessed much wetter conditions in the past. Natural variation in insolation, combined with various other
               mechanisms, gives rise to alternating arid and humid periods in North Africa, shifting approximately every

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