Deciduous tree leaves

The Value of Trees: 1 Introduction

The Word Forest Organisation is launching a new series of articles entitled ‘The Value of Trees’. Each piece in the series will explore a key ecosystem service delivered by forest ecosystems and explain how reforestation efforts in Kenya can enhance the ecosystem service benefits for the local community and improve ecosystem health on a national scale. Not only do we depend on healthy ecosystems for survival but they are also crucial in sustaining our global economy.

What are ecosystem services?

In simple terms, an ecosystem is a community of interacting organisms within a physical environment.

Ecosystem services are defined as the contributions of ecosystems to human well-being that directly or indirectly support our survival and quality of life [1]. Without healthy ecosystems we would not have access to drinking water, food or clean air [2]. Ecosystem services deliver both environmental and social benefits as a consequence of the relationships between biotic (living) and abiotic (non-living) processes (see Fig.1). As the population continues to grow, so too does our dependence on these ecological processes, regardless of where we live in the world. 

Although each ecosystem service will be analysed in isolation, it is vital to acknowledge the complex and interdependent relationships between services that have direct knock on effects upon one another [3]. For example, deforestation affects the water cycle; it leads to decreased rainfall which, in turn, has a negative impact on soil health and therefore reduces the  ability of the ecosystem to support crops.

Loss and damage to ecosystem services 

Land-change decisions dictate the number and quality of ecosystem services [4].  In order to meet the commodity demands of the expanding population, ecosystems have been transformed in the last few decades to support more people [5]. This has led to potentially irreversible damage to the structure and functioning of ecosystems, reducing the capacity for the delivery of ecosystem services [4]. The Millennium Ecosystem Assessment (2005) [6] observed that 60% of the ecosystem services examined are threatened by human activity [4], while between 1997 and 2011 land-use change alone promoted the loss of services accounting for US$4.3 trillion to US$20.2 trillion per year [4]. Human activities are most prominently impairing the flow of ecosystem services provided by forests, especially in the tropics [7]. This extensive study has stimulated debate and further research since its publication that has revealed the further loss of ecosystem services around the world.

The ecosystem service contribution of trees 

Forest ecosystems provide a plethora of ecosystem goods and services that cannot be effectively replaced by technology [8]. With careful spatial planning and after-care, trees can contribute to key environmental processes such as soil formation, nutrient cycling, water and climate regulation, habitat provision and pest control to name a few [2]. Trees also provide social benefits such as increased aesthetic value and ecotourism opportunities in the area. The establishment of trees in urban areas is especially beneficial; trees can mitigate the ‘heat island effect’ which occurs when concentrated human activity causes an urban area to become significantly warmer than its surrounding areas. As well as reducing the energy used for air conditioning and noise pollution, trees absorb harmful carbon dioxide emissions, a process pivotal to offsetting our current carbon output [7]).

Monetary value of these ecosystem services 

Because nature provides ecosystem services for free and most people lack knowledge of the importance of their delivery , it is easy to take them for granted [5]. Their value is often dismissed for these reasons. Highlighting the value of the services provided by nature is important in bridging the gap between environmental protection and economic growth [9].

In Kenya, much like the rest of the world, policy failures obstruct protection of forest ecosystems. Ecosystem services are key contributors to our well-being – this can be particularly important in developing countries where people tend to have less physical capital. They may not hold traditional economic value but, when they are lost, the costs, resulting from issues including increased occurrence of disease, poor soil fertility and operation of wastewater treatment amongst others, are huge. The UNEP stated that between 2000 and 2010 50,000 hectares of forest in Kenya’s Water Towers were felled for fuel-wood and timber of a volume of 250m3/ha, estimated to be worth USD 13.62 million [10]. However, losing the ecosystem services provided by these forest ecosystems were estimated to cost the economy USD 36.52 million per year – more than 2.8 times the revenue generated by deforestation [10].

Raising awareness and gaining better understanding of the benefits provided by forest ecosystems must be a priority if we are to maintain and protect them [9]. Policy tools that recognise the value of non-marketed forest non-use products such as climate regulation rather than just transactional tangible goods such as wood, need to be established with urgency.

Alice O’Grady and The Team

References:
[1] https://biodiversity.europa.eu/topics/ecosystem-services
[2] https://www.sciencedirect.com/science/article/pii/S1389934117300345
[3] https://www.pnas.org/content/112/24/7348
[4] https://www.enea.it/it/internazionali/relazioni-internazionali/cooperazione-allo-sviluppo/archivio/nexus/bibliografia/wwdr2015.pdf
[5] https://i.unu.edu/media/ehs.unu.edu/news/3890/resilience_academy_wp2.pdf
[6] https://www.millenniumassessment.org/en/index.html
[7] https://www.fs.fehttps://www.millenniumassessment.org/en/index.htmld.us/nrs/pubs/jrnl/2018/nrs_2018_nowak_002.pdf
[8] http://www.cifor.org/publications/pdf_files/Books/BNasi0201.pdf
[9] https://www.sciencedirect.com/science/article/pii/S2212041612000162
[10] https://www.unenvironment.org/news-and-stories/press-release/deforestation-costing-kenyan-economy-millions-dollars-each-year-and

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