Assessing ecosystem degradation related to anthropogenic and natural drivers
Leibniz Centre for Tropical Marine Research (ZMT)
In a recent publication we developed a conceptual framework to assess ecosystem degradation at the example of mangrove ecosystems around the globe. Depending on the context the term “degradation” has varying definitions, which makes it often difficult to identify, quantify, and characterize the status and potential degradation of an ecosystem. Ecosystem status assessments generally emphasize areal change (gains/losses) as a primary indicator. However, this over-simplifies complex ecosystem dynamics and ignores other relevant factors. Therefore, a conceptual framework was developed to: i) examine drivers of ecosystem degradation and characterize system status, and ii) delineate the roles of biogeographic and geomorphic variability, site history and typology, and references. Many of the anthropogenic drivers are related to hinterland dynamics and coastal development. The universal applicability of the framework is demonstrated through a series of case studies that represent locations with differing drivers of degradation and biogeographic and geomorphic conditions. I will explain the concept at the example of one of the case studies, the Indonesian Segara Anakan Lagoon, a heavily degraded mangrove-fringed coastal lagoon that was studied in the frame of the SPICE programme (Science for the Protection of Indonesian Coastal Ecosystems) over more than a decade. This conceptual framework facilitates scientists, conservation practitioners, and other stakeholders in considering multiple aspects of ecosystems to better assess system status and holistically consider degradation. Users are encouraged to adapt this framework for their own systems of interest to provide data-driven, objective assessments that can inform and re-equilibrate management and policy actions in the face of ecosystem degradation and loss.
Figure © Tim Jennerjahn
Geochemistry and mineralogy of sediments along the transboundary Umba River as indicators of provenance and weathering
Amon Kimeli1,2, Oliver Ocholla2, Judith Okello2, Nico Koedam3, Hildegard Westphal1, James Kairo2
1) Leibniz Centre for Tropical Marine Research (ZMT), 2) Kenya Marine and Fisheries Research Institute (KMFRI), 3) Vrije Universiteit Brussels
The transboundary Umba River traverses two countries, with its source in Usambara Mountains in Tanzania and draining its water to the Indian Ocean in Vanga, Kenya. Umba River delivers freshwater, nutrients and terrigenous sediments to the Indian Ocean passing through the estuarine mangrove forest of Vanga. Knowing the connectivity and influence of the larger Umba River catchment on the downstream coastal biotopes is therefore vital. It is also from this basis that Kenya and Tanzania have jointly proposed the setting up of a transboundary conservation area (pTBCA) stretching ~100 km along the coastline from Diani, Kenya in the north to Tanga, Tanzania in the south. The pTBCA is based on high biodiversity, contiguity, shared resource and the possible influence of the larger Umba River and the need for catchment-wide resource conservation and management. The chemical and mineralogical distribution and composition of fluvial Umba River sediments were analyzed and evaluated to describe their source characteristics, degree of weathering, provenance and fate. The Umba River catchment is characterized by outcrops of the granitic Precambrian basement and the quartz-dominated Paleozoic Karoo Supergroup, overlain by Mesozoic and Cenozoic sediments. Based on the chemical index of alteration, the Umba River sediments indicate a moderate to high weathering. They are also rich in both mafic and felsic minerals characteristic of the source geology and the lithologies it drains. Additionally, the similarity of minerals in the Umba River sediments collected both in the upper catchment (close to source) and downstream (in the estuary and coastal area) indicate a uniform source. They also indicate the effects of transportation in their grain sizes and shapes.
Blue Economy in Bangladesh: Missing ‘Social Equity’ issues in policies
Jewel Das1 and Marion Glaser1
‘Blue Growth’ or ‘Blue Economy’ supports sustainable livelihoods and food security globally and the demand for its mainstreaming is also reflected in the Sustainable Development Goals (SDGs). The Bangladesh government adopted this concept in their 7th five-year plan and initiated investments in coastal sectors. This brings changes in the social-ecological systems of coastal Bangladesh. Understanding potentials of Blue economy also necessitates operative inclusion and dynamic involvement of all societal groups. Our study examines scientific literature and evidence on the links between blue growth and social inequality. Based on an initial literature review, we find that blue economic growth in Bangladesh can lead to social inequality and generate conflicts among resource users. Particularly, small-scale fishers along with other coastal residents may experience displacement, unjust and inequitable distributions of coastal and marine resources, and costs and benefits associated with change. This generates diverse conflict potentials. To mitigate, resolve or transform ocean use conflicts and ensure effective governance, we recommend blue economy policy-making should address ‘social equity’ to render the blue economy outcomes more equitable and thus long-term sustainable in Bangladesh. This work analyses different types of published literature associated with blue growth and social equity for coastal poverty worldwide.
Hydrogeological system analysis of the freshwater lens of Gili Air (Lombok, Indonesia)
AG Submariner Grundwasserabflus, ZMT
Gili Air is a very small Island (1.73 ) coral reef on the north-western coast of Lombok, Indonesia. It is part of the Gili Islands, a hotspot for Indonesia’s tourist industry. Gili Airs aquifer contains freshwater, unlike the neighboring islands, and the island’s tourist industry and population are partly dependent on groundwater supplies. Small coral reef islands can form a fresh groundwater body in a lens-like structure, which is susceptible to variations in the water budget. We investigated the general hydrogeological system of Gili Air with simple field methods and estimated the volume and recharge of the freshwater lens. The results of this work endeavour offer a first and solid base for future research surrounding this topic.
Global assessment of coastal renewable freshwater resources
Sara Nazar1, Nils Moosdorf1,2
1) Submarine Groundwater Discharge, Leibniz Centre for Tropical Marine Research (ZMT), Fahrenheitstraße 6, 28359 Bremen, Germany. 2) Institute of Geosciences, Kiel University, Ludewig-Meyn-Straße 10, 24118 Kiel, Germany
Coastal zones are considered one of the most vibrant regions of the earth. They protect many habitats and ecosystems and favour human settlements. The last decades have seen a growing trend toward altering the hydrology of watersheds draining to the coast because of climate change, land-use change, water overexploitation, and unsustainable developments. Overuse of coastal freshwater resources leads to depletion and quality degradation. In coastal settings, groundwater is particularly vulnerable because saltwater can contaminate the aquifer and render it unusable. Thus, a fundamental question has arisen in the coastal hydrogeology science field: How to manage coastal water resources sustainably.
For sustainable resource management, a safe operating space is required. Safe operating space determines a reliable boundary for human use, which will not stress the resource. In this research, a safe operating space is defined as the amount of renewable water storage. While the water abstraction is less than the renewable storage, freshwater resources are not stressed.
To estimate the renewable water storage, the catchment water budget is calculated, which can be simplified as differences between total precipitation and total evapotranspiration. The water budget is measured annually from 2001 to 2020 for more than 40,000 coastal catchments on the globe. Temporal trends have been assessed with the application of linear regression. The results showed significant trends in less than 15% of coastal catchments, including significant increases and decreases. Additional features such as water abstraction will be implemented to analyse whether the coastal water resources are stressed.