Objectives

Studying fragile land cover is essential since it increases awareness and reveals the formation mechanism of those lands (Jiang et al. 2011). The combined impact of agricultural land expansion and invasive plantspecies threatens the sustainable supplies of ecosystem services. The impact is highly aggravated in fragile lands in steep mountainous areas and drylands since the people living in these areas are highly vulnerable and have low capacity to respond to environmental hazards. Therefore, assessing cover types that are detrimental forsustainable supplies of ecosystem services in fragile lands is timely and relevant to recommend solutions for sustainable land management.

The main objective of the dissertation is to assess two major land cover types detrimental for ecosystem services in fragile lands of Ethiopia. The main reason why Ethiopiawas chosenfor the casestudies is due to the ongoingpressure on fragile lands of the country which is triggered by population growth, large-scale agricultural land acquisition and problems arising from invasive species. The specific objectives are: i) Explore opportunities and challenges of remote sensing applications in assessing ecosystem services ii) Map the extent of Prosopis juliflorainvasion of the Awash Basin of Ethiopia and iii) Assess undercover cropland inside forests of the Bale Mountains of Ethiopia. To achieve the main goal of the research, three major studies were carriedout.

Study 1 Identifying applications of remotesensing inquantifying andmapping ecosystem services Globally, there is a growinginterestbydecision-makers andscientists to quantitatively estimate the benefits of nature to humans. Such quantitative assessments require fast and cost-effective tools that enable to generate reliable information at various scales.

Remote sensing is oneofsuch tools that is recently being realizedfortheirapplicability inquantifying andmappingecosystem services (e.g.Krishnaswamyetal.2009;Fenget al. 2010). Remote sensing technologies can thus be highly relevant in large-scale

different scales bysystematicallyreviewing literature in the past. The major themes in this study are listed below.

 Identify remote sensing data and approaches that are used in quantifying and mapping ecosystem services;

 Identifyimportantfactors thatneed to be consideredinselectingsuitable remote sensing data and methods for quantifying andmapping ecosystem services; and

 Discuss examples of remote sensing applications for quantifying and mapping ecosystem services and identify research gaps that are relevant to the topic.

Study 2 Prosopisjuliflora invasion and its impacts on ecosystemservices

Exotic species are oftenintroduced to a given locality for the benefits theyprovide to the society.However,introduction of a newspecies notalwaysachieves the intendedgoals since a species could become invasive and threaten supply of ecosystem services. P.

juliflora is one of such species was introduced to provide ecosystem services (e.g., breaks to stopwinderosion),but has widelybecome invasive in those regions,because ofits characteristics (e.g.deeprootingsystem, fastgermination andcoppicing capacity). Thus,it is essential to mapinvaded areas with remotesensingandassess the potential impacts of invasion on ecosystem services. In this study the potential risks of introducing a species to new vicinity were explored using P. juliflora invasion in the fragile lands of the Afar Regional State of Ethiopia as anexample. The mainfocuses of this study are:

 Quantifying & mapping of P. juliflorainvasion and assess its temporal dynamics;

 Identify and discuss the impacts of the invasion on selected ecosystem services;

 Identify the major challenges in the management of P. juliflora invasion and recommend possible solutions.

Study 3 Undercover cropland inside forests:revealed with remote sensing and field observations Being driven by the ever increasingglobal demandfor food, cropland has been largely expanding worldwide. Recently, this is an ongoing process especially in tropical and subtropical countries particularly in the Sub-Saharan African countries. Large-scale agricultural land expansion is taking most of the flat-terrains that are suitable for mechanized agriculture which in turn led to shifting of the land that is used by local small-scale farmers.Since the producedcropfromlarge-scale farms is mainlyforexport,

small-scale cropland continued to expand to feed the increasingpopulation to the extent fragile lands that were previously marginalized are nowadays cultivated.

Due to desperate need for growing crops new patterns of cropland expansion emerge and/or old traditional systems such as agro-forestry are adopted in new areas where they were previouslynotpracticed.Where there is restriction inclearingofforest lands inmountainousareas,secretlygrowingofcrops inside forests (undercover cropland) is becoming a commonphenomenon.The hidden(undercover)croplandinside forests are not direct replicates of traditional agro-forestry systems since we assume that farmers use them just as a point of entry to own a new cropland by gradually and secretly degrading the forest which will finally be converted to agricultural land. To ensure sustainable resource use andmanagement,understanding the patterns ofsuch complex systems and the variables that influence them is essential.

In this study, the patterns of undercover/hidden cropland inside forests and its influential factors were assessed using combination of remote sensing and ground surveying data based on a case studysite inthe Bale Mountains ofEthiopia. The major issues addressed here are:

 to map the general patterns of cropland in the Bale Mountains of Ethiopia and identify the hotspots of cropland under forest canopies;

 identify explanatory variables of undercover cropland in the region, and

 discuss the emergingchallenges andfuture prospects of the undercover cropland.