Getting the balance right in Paradise

Getting the balance right in Paradise

Island ecosystems have fascinated people, particularly natural scientists, for centuries. Isolated from mainland continents, islands provide a unique and often fragile “template” for the provision of ecosystem services such as their unique genetic resources – namely the highly endemic flora and fauna, formed over millennia as a result of isolation. However island ecosystems are altered and threatened by humans once they are colonised. Very special considerations are needed to strike a balance in the trade offs between provision of different types of ecosystem services and human well-being on these paradisiacal places.

The Fortunate Islands

Macaronesia, meaning the happy or fortunate islands, (Makaros = happy, nesia = islands), was the word first used by the English botanist Philip Webb to describe the volcanically derived archipelagos of the Azores, Madeira, the Canary Islands and Cape Verde during his studies on their lush plant communities.

Today, Macaronesia houses the largest remaining area of relict Laurissilva rainforest in the world. Global Quarterny Era (Pleistocene) cooling and glacial expansion caused extensive glaciations resulting in the extinction of extensive laurel forest communities on the European mainland. However, remnants of these now relict forests persisted on many Macaronesian islands where the climate remained more stable.

The ecoregion of Macaronesia and the Rede Natura 2000 protected areas of the Madeiran archipelago. The relict Laurissilva rainforest on the largest island – Madeira - has UNESCO World Heritage status.

Madeira, one of the largest and oldest macaronesian islands, houses the largest remaining intact area of laurissilva (approximately 15 000 hectares) which is situated mainly on the north of the island between 600 – 1300 metres altitude – a result of systematic clearance following the island’s colonisation. However, the laurissilva is now protected: it is a classified Biogenetic Reserve under the Habitats Directive and was declared a UNESCO World Natural Heritage site in December 1999, a source of immense pride for all Madeirans.

The Laurissilva - a massive and unique Green Infrastructure

The laurissilva is a relict rainforest, a complex and dynamic community that acts as a massive green infrastructure. A green infrastructure is a natural or semi-natural area with ... "environmental features designed and managed to deliver a wide range of ecosystem services such as water purification, air quality, space for recreation and climate mitigation and adaptation". The laurissilva does all of these things and more.

The Millennium Ecosystem Assessment (MA) was carried out between 2000 - 2005 to “assess the consequences of ecosystem change for human well-being and to establish the scientific basis for actions needed to enhance the conservation and sustainable use of ecosystems and their contributions to human well-being”. Ecosystem services are the link between ecosystem processes and human well-being – and are classified into supporting, provisioning, regulating and cultural ecosystem services –according to the type of "job" they do and how it can benefit us.

In short, Ecosystem Services are the goods and services provided by ecosystems that benefit, sustain and support the well-being of people. Set in the context of an island ecosystem, the laurrisilva is the beating rain-fed heart of ecosystem service provision. But is there a balance in the trade-offs between the different types of services?

The supporting services provided by the Laurissilva are a given. Plants are primary producers; the decomposition of plant matter together with erosion of the volcanic deposits form soils that contribute to the local nutrient cycle. Particularly important laurissilva provisioning services - especially from a freshwater ecologist’s point of view – are freshwater and genetic resources. The laurissilva has both of these in spades but this is where some of the problems concerning balance start.

Madeira’s freshwater, entirely derived from precipitation and low cloud cover, is intercepted by the all-important laurissilva which is situated at mid to high altitude on this massive basaltic outcrop, sitting in the north Atlantic. Recognised as a Biogenetic Reserve, this relict rain forest and its aquatic and terrestrial entomofauna have very high levels of endemism, formed over thousands, if not millions of years of isolation. Well over 1200 indigenous plants are known from published checklists, including endemic species, sub-species and varieties and I’m sure the number is constantly rising.

In checklists published over a decade ago through the local museum , I estimated approximately 26-28% endemicity within the insect dominated freshwater macroinvertebrate fauna. Results from recent studies on the macaronesian mayfly fauna (Ephemeroptera) indicate that this is a considerable underestimate (and that the checklist must be updated), especially if cryptic species predominate within the macroinvertebrate fauna. However, the loss of freshwater habitats through long term human intervention has almost certainly resulted in the permanent loss of biodiversity and unique genetic resources from the laurissilva. The diversity of the island’s genetic resources contained within the laurissilva is a fundamental component of biodiversity which is fully recognised under the international Convention on Biological Diversity. The loss of endemic species means that unique information stores of evolutionary history, which have been passed on (inherited) via DNA from one generation to the next, are irretrievably lost.

Madeira has a dense network of streams (the blue lines). Most of the flow is diverted into levada channels (the red lines)

Madeira is blessed with plentiful freshwater and a dense drainage network of over 200 small streams and rivers. It is this plentiful resource and its intimate association with the laurissilva - Macaronesia's own unique green infrastructure - that lies behind Madeira’s successful colonisation by Man. The figure of the island of Madeira (see above) illustrates just how rich this small volcanic island is in streams and rivers – shown as the blue lines. You’ll also notice long red lines cutting across the catchments and the streams. These are the levadas, a network of man-made irrigation channels that intercept water at or close to source and transport it across catchments to other areas of the island for crop irrigation, potable water supply and hydroelectric power generation. The very first levadas date from Madeira’s colonisation, hewn into the rock face through the dense laurel forest. Madeira’s main levadas form over 650km of channels, transferring ground and surface water from altitude in catchments where water supply is plentiful (mainly in the North) to areas where water is scarcer, mostly on the South of the island. The entire network is estimated to be well over 1000 km long.

The levadas carry water from altitude to lower lying areas where it is used for agriculture, domestic supply and hydroelectric energy production.

However, the levadas have come to serve another important function as the socio-economic fabric of Madeira has shifted. They are providers of cultural ecosystem services such as a sense of place, recreation and ecotourism. The levada network attracts tourists (thereby generating important revenue) and Madeirans alike – allowing them to travel into the heart of the laurissilva. Levadas are used for hiking, BTT biking, birdwatching, plant spotting, landscape photography and experiencing first-hand the island’s unique landscape, habitats and biota. Radical sports such as canyoning take place in the gorge-like streams. These services and associated activities contribute to constituents of well being, particularly health and access to basic material for a good life. Being outdoors and outdoor activities promote physical and psychological well-being which is important in preventative health care, reducing costs on notoriously overstretched national health systems in the long-term.

The Millenium Ecosystem Assessment Report highlighted links between ecosystem services and human well-being.

The word “Levada” is derived from the Portuguese verb “levar” which means “to take”, “to carry” or “to take away” and this is precisely what the levadas do. Although a fundamental part of the Madeiran human landscape, the levadas divert massive amounts of water away from important natural ecosystems – namely the springs, madicolous habitats and streams. As a result, most madeiran streams have drastically reduced flow and even no flow at all along considerable reaches of the channel.

If you look at the three photos of the streams below, you will notice the small size of the wetted channel relative to entire channel width – this is due to flow being diverted into the levada systems. This impact exerts a massively detrimental effect upon the freshwater habitats and biota. Reduced flow means less habitat availability and resources, such as food, for endemic freshwater species. This can result in extinction or highly threatened status - and irreplaceable loss of part of the island’s unique and precious biogenetic reserve. The number of endemic freshwater species that have disappeared since the construction of the levadas can only be guessed at. Climate change impacts may accelerate that loss. This is a "trade off" between ecosystem services that is of great detriment to macaronesian genetic resources.

Madeira's streams house many endemic species of insects and plants. However, the reduced flow threatens the island's biodiversity.

Research on Macaronesia’s mayfly fauna has shown that many of the newly discovered endemic species are highly restricted in their distribution. Is the reduced flow regime in natural stream habitats limiting their potential distribution and could this be exacerbated by climate change effects? These questions deserve to be looked into considering the UNESCO status of the laurissilva. The last collecting trip I made to the island in late 2013 was fraught with difficulty to find specimens for subsequent molecular analyses; flow levels were extremely low at some sites that I had collected from for years. I was told that it had been an exceptionally dry year, with serious wildfires in areas planted with exotic vegetation (being a rainforest - laurissilva is comparatively fire resistant). The implications for other highly endemic groups, such as the caddisfly (Trichoptera), which have very distinct seasonal and spatial distribution patterns in Madeira’s freshwater, are just as worrying.

There is growing and understandable support to propose that the levadas of Madeira be granted UNESCO world cultural heritage status. They are an unmistakable and emblematic testament to the history of the island’s colonisation and have immense economic, historical and cultural importance. Their link to human well-being is evident, but there has to be a balance between the island’s natural and cultural heritage to ensure robust links between well-being and the ecosystem services provided by the laurissilva are maintained - particularly for freshwater, biodiversity and genetic resources.

Basic measures such as the implementation of environmental flow regimes are a step in the right direction - allowing the streams of Madeira to maintain and even better - improve the state of their highly endemic communities and ecosystem function. By returning at least some of the diverted water from the levadas to the island’s stream via environmental flow regimes a win-win situation is attained and the “floating garden” - as Madeira is known - will better preserve an important part of its unique genetic resources, strengthening further the laurissilva’s deserved status as a classified Biogenetic Reserve under the Habitats Directive.

I'm aware of the fact that I haven't considered regulating ecosystem services provided by the laurissilva in this particular blog, but I'll come back to them and the other considerations in a future blog. In the meantime, get up, get out and go and enjoy nature!