E L SECRETO DEL MAGO

Anthropogenic climate change is just one of the stressors affecting global biodiversity, agriculture and water resources. Climate change will interact with these other stresses and therefore they must be considered in conjunction, rather than as acting in isolation (Root et al., 2003). This section will present the main human-induced stresses that need to be considered alongside global climate change.

2.5.1 Population Growth and Urbanisation

Although climate change will be a key driver for many changes to future water supply and demand and potential biodiversity losses, there are other factors which will be influential. Firstly, population change will alter future water demand.

Frederick and Major (1997) argued that, in the future, population growth will be the most important factor in determining the availability of water in the developing world. Vorosmarty et al. (2000) support this, arguing that population changes and economic development will be more important than climate change for water availability. World population is expected to continue to grow, with much of this growth in developing countries, in particular in urban areas. Increasing the number of people relying on limited water resources will lead to additional pressure on sustainable management strategies. Flörke et al. (2018) found that global urban water demand could increase by around 80% by 2050 and that one in six large cities is likely to be at risk of water deficits. As countries develop, more people tend to move to urban areas in search of better living conditions and economic

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opportunities. The size of the urban population in East African countries is likely to continue to increase in the future, placing more pressure on limited water

resources (Douglas et al., 2008). Therefore, demographic change must be considered in conjunction with climate change when examining the future of natural systems.

2.5.2 Land Use Change and Degradation

Land use and cover is constantly changing across the entire world, as a result of multiple drivers and impacts, which can contribute to climate change and

biodiversity loss (Houghton et al., 2012; Willcock et al., 2016). The greatest global change in land use has been towards more agricultural land. Krausmann et al. (2013) estimate around one third of the terrestrial land surface is dedicated to agriculture. In addition to agriculture, other demands on land, such as urbanisation and bioenergy, are expected to increase in the future (Van der Esch et al., 2017). Land degradation is extremely difficult to quantify. Van der Esch et al. (2017) argued that the degree to which land use practices, particularly agricultural practices, degrade land is very uncertain.

Romanowicz and Booij (2011) argue that one of the biggest challenges in current hydrological research is assessing whether changes to water availability are caused by climate change or land use change. Models are used to assess the impacts of historical and projected future land use changes as well as changes in climate (Thanapakpawin et al., 2007; Huisman et al., 2009). Some previous studies have found that combining land use and climate changes can lead to the two effects cancelling one another out (Yan et al., 2016; Zhang et al., 2016). However, Hejazi and Moglen (2008) argued that the combination of land use and climate changes might result in more substantial hydrological changes than either driver alone. This demonstrates the complexity of climate and land use changes. Therefore, the combination of effects of land use and climate change is still an important topic of research.

2.5.3 Habitat Fragmentation and the need for Wildlife Corridors for Biodiversity Protection

Habitats are becoming increasingly fragmented as a result of human development. As settlements and agriculture expand, more land is converted from its natural vegetation. In addition, road and rail networks cut across the landscape, splitting areas of similar vegetation into smaller fragments. Increasingly fragmented

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habitats will limit species’ abilities to respond to climate change by migrating. Although many species are likely to need to shift their range to respond to climate change, increasingly isolated fragments of suitable habitats will make movement more difficult for many species. Wieczkowski (2010) argues that species that remain in isolated habitat fragments will begin to experience other negative

effects, including a reduction in natural genetic variation within the population and even local extinctions.

Preserving wildlife corridors can facilitate species movement across the landscape. Wildlife corridors are defined as narrow strips that link at least two larger habitat patches. Jones et al. (2009) also show the importance of maintaining connectivity within landscapes, particularly between conservation areas, for

reducing pressure on ecosystems and encouraging demographic links and gene flow. However, detailed knowledge of important wildlife corridors in many countries is still lacking. Perre et al. (2014) highlight the knowledge gap on wildlife corridors in Africa, showing that those which have been identified have focused on large species.

2.5.4 Invasive Species, Weeds, Pests and Diseases

Invasive species are non-native plants or animals that have been introduced to environments and are causing harm to the existing ecosystem. Biodiversity and agricultural systems are impacted by invasive species, which may increase the vulnerability of these systems to climate change. Roy et al. (2017) shows that one quarter of the world’s most invasive species have environmental impacts that have been connected to diseases in other wildlife. Oerke (2006) found weeds caused more damage than pests and diseases, but that the total losses vary between crops. Porter et al. (2014) note that the effects of CO2 fertilisation that are

projected to benefit crop production will likely also benefit invasive weeds. In addition, warmer winters and the earlier onset of spring could allow some parasites to survive more easily. A shift in climate could lead to pathogens and diseases moving into new areas. These negative impacts on agricultural systems could also lead to threats to human health.

2.5.5 Impacts of Policy

Policy and management practices will have a significant impact on water

resources biodiversity and agriculture in the future. In recent years, the volume of climate change relevant policies and legislation has increased dramatically. At the

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national and international levels, there are several important climate policies and targets. The Sustainable Development Goals (SDGs) are 17 global social and economic development goals set by the United Nations. These goals replaced the Millennium Development Goals which ended in 2015 and are statements of

ambitions rather than legal obligations. SDG13 aims specifically to combat climate change, but there are also other SDGs which are relevant to climate change action. SDG15, ‘Life on Land’, focuses on the sustainable use of ecosystems and protection of biodiversity and SDG14 covers marine species and coastal

biodiversity. In addition, SDGs also relate to water (SDG6 on clean water and sanitation and SDG12 on the responsible consumption of natural resources) and agriculture (SDG2 on reducing hunger).

In 2015, the Paris Agreement was adopted at the United Nations Framework Convention on Climate Change (UNFCCC) in Paris twenty first Conference of the Parties (COP 21). This reaffirmed commitments to limiting global temperature rise to 2°C above pre-industrial levels and even potentially limiting to 1.5°C. In

addition, the Paris Agreement calls for a reduction of net anthropogenic GHG emissions to zero during the second half of the century (Tanaka and O'Neill, 2018). The Paris Agreement requires each Party to prepare nationally determined contributions (NDCs). These NDCs include the national efforts that the country will take to reduce emissions and adapt to climate change. However, they currently fall short of the emissions reductions necessary to meet the temperature threshold targets (Rogelj et al., 2016). The NDCs would currently lead to global temperature increases of between 2.7°C and 3.2°C (Rogelj et al., 2016). The Paris Agreement is now recognised as a turning point in global efforts to deal with climate change. However, immediate mitigation action may be needed in order to meet the targets. Arnell et al. (2013) found that even if emissions had peaked in 2016, most effects of climate change, both positive and negative, at the global scale would not have been avoided by 2050s. Policies were found to delay the impacts but negative impacts would still occur.

The National adaptation programmes of action (NAPAs) were created by the Least Developed Countries (LDCs) to identify priorities for adapting to climate change. Similarly, Nationally Appropriate Mitigation Actions (NAMAs) were developed. In addition to climate change policies, there are a number of international

agreements and conventions that focus on protecting biodiversity, which are also relevant to this work. The Convention on Biological Diversity, the Convention on

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Conservation of Migratory Species and the Ramsar Convention on Wetlands aim to conserve the world’s species and ecosystems.