What is known as a group of individuals of the same species present in an area at a given time in Assamese?

7.7.7 Ecotones

Ecotones are abrupt changes in vegetation (Walker et al., 2003) or two adjacent, different and homogeneous community types, producing a narrow ecological zone between them (Attrill and Rundle, 2002). Ecotones are used to define basic units in landscape studies, and their identification relies on the sharpness of the vegetation transition, particularly ecological conditions and their causes (i.e., natural or anthropogenic environmental change, invasion or alteration of species present) (Walker et al., 2003). Ecotones are dynamic, sometimes with strong fluctuations. In the littoral zone of a lake, an ecotone is the transition zone of distinct aquatic communities that varies throughout the year according to seasonality (Attrill and Rundle, 2002). As Critical Zone research expands, scale will play a more and more important role. This will lead to the development of Critical Zone concepts similar to the ecotone concept in landscape ecology.

Introduction

Wetlands are ecotones (transition zones) between terrestrial and aquatic environments. They make up a myriad of landforms that are inundated or saturated by water, part or all of the year, and support specialized vegetation adapted to such conditions. In the US alone there are more than 90 names used for wetlands, and while some are familiar (bog, bottomland, fen, moor, mangrove, marsh, peatland, tundra, swamp, etc.), differentiating between others is a specialized science. Neither land nor sea, human interaction with wetlands often seems a study in contradictions. Wetlands have frequently sported two opposing facades: on the one hand, the marshes of Mesopotamia are thought to be the inspiration for the Garden of Eden in the Old Testament. On the other hand, the mythical battle between Hercules and the Hydra in the Greek swamps of Lerna is viewed as a metaphor for the struggle to reclaim wetlands and make an insalubrious environment more amenable. Like all landscapes, human perception and interaction with wetlands have changed as a result of alterations in demography, economy, environment, and technology. In response to widespread destruction of wetlands through reclamation in the past 150 years, wetland preservation, mitigation, and restoration have become major societal preoccupations seeking to reverse destruction and promote biodiversity and water functions (Figure 1).

13.2.3.4 Tundra—Treeline

The treeline ecotone is the transition zone between a closed canopy, upright forest and low growing, primarily herbaceous tundra. We emphasize the ecotone as a zone, rather than a line, because any line one could identify is more scale dependent and has less ecological meaning. The ecotone occurs on mountain slopes as the alpine treeline and at high latitudes as the Arctic treeline (even in Tierra del Fuego the treeline seems to be determined by altitude (Cuevas, 2002)). At global scales, the latitudinal and elevational limits of trees are controlled by temperature. The limitation is either direct damage by frost, a lack of energy that does not allow individual plants to accumulate enough carbon via photosynthesis to form a tree (e.g., Cairns and Malanson, 1998), or, as more precisely demonstrated, at lower temperatures plants are not able to reallocate the energy they can gain in photosynthesis sufficient to form a tree (e.g., Körner, 1998). At finer spatial scales other factors, particularly geomorphology and available water for photosynthesis, could also be limiting factors (Malanson et al., 2011); however, at the scale where the ecological response may be considered a disaster, the focus should be on temperature (e.g., Billings and Peterson (1992) noted the importance of melting and eroding thermokarst for effects in the Arctic). The resulting hypothesis is that as climate warms, trees will move upslope and to higher latitude.

We have good evidence that such geographic responses have occurred in the past (Webb, 1992; Lloyd et al., 2002). Although the retreat of continental glaciers following the Late Glacial Maximum allowed trees to expand poleward, the details of the connection to climate are only seen at millennial or finer temporal scale. More recently, observations of current treelines using tree rings and of somewhat older treelines using dead trees indicate that the ecotone can fluctuate with changes in global climate (e.g., Lloyd and Graumlich, 1997; MacDonald et al., 1998).

The advance of tree cover upslope or to higher latitude also has some implications for climate change itself. Trees will absorb and store more carbon than do tundra plants. Thus, this response could have a negative feedback on the driving force of climate change. However, the strength of this feedback is not well quantified. The rise of alpine treelines to higher elevations would amount to a minor effect, given that the area is limited. A shift in latitudinal treelines could be more significant in the northern hemisphere. Northern forests are an important store of carbon, and through increase in biomass and soil organic matter have absorbed a significant amount of the carbon released by the burning of fossil fuels over the past two centuries. A northward expansion could increase this effect. Another feedback, a positive one, is that forests have a lower albedo than tundra. Absorbing more radiation over a larger area, they can contribute at least locally to warming—and thus to their own expansion.

Although the transition zone between trees and tundra has been the focus of research on possible ecological impacts of climate change, recently the role of shrubs has received more attention (Naito and Cairns, 2011). Although some tundra is clearly recognized as dominated by shrubs, the potential for the expansion of shrubs to replace herbaceous tundra could be an outcome of climate change. This expansion could affect carbon storage and albedo, but with lower canopy depth probably less than trees, but it also has effects on snow cover (Myers-Smith and Hik, 2013).

To further illustrate the effects of climate change on the treeline ecotone, we examine a single species, whitebark pine (Pinus albicaulis), as an example of the multiple factors of ecological response to climatic change (Tomback et al., 2001). Whitebark pine is a keystone species and plays an important role in maintaining ecosystem functions in subalpine environments. The large, highly nutritious seeds of the whitebark pine provide a vital food source for many species, including the threatened grizzly bear (Ursus arctos horribilis), Clark's nutcracker (Nucifraga columbiana), and other birds. The tree occupies high-elevation sites, often in steep, rocky areas, and serves to increase slope stability and soil formation in those sites. Individuals and small groups of whitebark pine provide rare shelter in those sites, blocking wind, and shading underlying snow which impacts the hydrology and succession. At higher elevations in undisturbed sites, whitebark pine communities may persist for more than 1,000 years. Among the threats to whitebark pine are mountain pine beetle (Dendroctonus ponderosae), white pine blister rust (Cronartium ribicola), and replacement by successional species as a result of fire suppression, all of which are impacted by climate change.

The mountain pine beetle spends the majority of its lifecycle as a larva feeding in the phloem tissue of pine trees. The host trees are eventually girdled and killed (Amman and Cole, 1983). Beetle survival and growth is sensitive to temperature, and outbreaks have been correlated with shifts in temperature (Powell and Logan, 2005). Climate change may affect beetle infestations through increasing drought stress, which inhibits the ability of trees to defend against the beetles, and warmer winters that may increase winter survival for the beetles. Predictions from population models suggest that range expansion will occur as beetles will be able to survive at higher latitudes and elevations in the coming century (Bentz et al., 2010). Range expansion into higher elevation forests will allow beetles to infect more whitebark pine, a species that has not evolved any defenses against the beetles (Raffa et al., 2008). Changes in forests will have secondary consequences (Saab et al., 2014).

Whitebark pine is unique in that has a mutually beneficial, even dependent, relationship with the Clark's nutcracker. The bird is dependent on the whitebark pine for food, has profoundly influenced the ecology and evolution of the pine as the tree is dependent on the nutcracker for seed dispersal, and hence the birds are responsible for locating many of these trees (Hutchins and Lanner, 1982). Clark's nutcrackers can store over 30,000 whitebark pine seeds in a mast season (Tomback, 1982): a number exceeding its nutritional requirements. The bird caches seeds at a depth of approximately 2 cm, often in the shelter of rocks, in sites compatible with germination requirements (Tomback, 1982).

White pine blister rust (WPBR) is a stem rust introduced from Europe early in the nineteenth century, and has spread throughout the ranges of the five-needled pines (including white, sugar, limber, and southwestern white pine). The fungus enters white pines through needle stomata and erupts as sport-producing cankers commonly on upper, cone-bearing branches, and tree mortality occurs through girdling or following the loss of branches from multiple cankers (Hoff and Hagle, 1989). Mortality can take many years in a mature tree; death can be hastened by pine beetle infections, root diseases, and other pathogens (Krebill and Hoff, 1995).

WPBR has the potential for causing local, if not global, extinction of whitebark pine (Kendall and Keane, 2001; Tomback and Achuff, 2010). The spread of blister rust and infection in whitebark pine is an intricate process, though small climatic changes, including an increase in the frequency of extreme precipitation events, could accelerate the spread of WPBR through whitebark pine habitat (Koteen, 2002). Changes in temperature, precipitation, relative humidity, and soil moisture influence sporulation and colonization of fungal diseases (Lonsdale and Gibbs, 1996; Smith-McKenna et al., 2013). Mortality from WPBR, warming and associated increased evapotranspiration, related changes in the fire regime, and competition from lower elevation species would push the whitebark pine to higher elevations (e.g., Millar et al., 2004). As with all species occurring at high-elevation, mountain peaks serve as a hard limit to the species' ability to move uphill to find habitable sites, and even at treeline WPBR is a threat (Tomback and Resler, 2007).

Abstract

Wetlands are the ecotone with rich ground for the aquatic and terrestrial flora and fauna. Wetlands are considered to be a natural ecosystem solution to extreme climate change. Climate resilience reflects as one of the prominent regulating services of wetlands. These are the unique ecosystems providing the unique services to the mankind. Water and its quality are the main factors for regulating the environment of wetlands. Unfortunately, wetlands like any other ecosystems are facing the threat from the increasing population and pollution. Over one such factor responsible for the deterioration is the impact of climate change. The changing climate due to the rise in the greenhouse gases particularly carbon dioxide has also impacted the functioning of the wetlands. Coastal wetlands likewise mangroves are the meeting points of fresh and marine aquatic environment. We know the water bodies around the globe are the worst-hit areas due to climate change and wetlands are no exception to this. On the other hand, the droughts affect the water level of these wetlands leading to their shrinkage and in turn the biodiversity of wetland ecosystem are the worst hit. The wetland ecosystem is significant for various functions such as food storage, water resource, pollution abatement, and the aquatic life, etc. It provides habitat for different species of flora and fauna along with various ecosystem services like environmental protection, pollution mitigation, and protection from cyclones, floods as well as local community livelihood. As the condition of wetland ecosystem of any particular region can give a glimpse of its conservation and management trend. Thus, the significance of the wetlands has been explained through one of the case studies from northeastern part of India. This case study highlights the understanding of climate change aspects related to the lake “Son Beel, wetland, the most significant wetland of Assam in particular and North East India in general with a great potential as Ramsar site designation for its great resource value and by ecosystem services. Son Beel offers a diversity of ecosystem services, which can be directly interlinked with the livelihood. Son Beel wetland is an essential natural infrastructure of disaster risk reduction offering flood mitigation and ensuring water security by recharging under-ground water Communities” access benefits in various ways viz. water, erosion check system, potable water, waste management, climate change policy, and Disaster Risk Reduction. Local inhabitants and communities have deep sacred beliefs in Son Beel because it protects them from the terrible risk of frequent floods and drought every year. People access nonmaterial benefits by spiritual, cognitive developmental, reflectional, recreational, and esthetic values. There is a need to ensure that wetland conservation, judicious use, and restoration are an integral part of sustainable development goals (SDGs) planning and implementation. Integrating wetlands services and benefits in Nationally Determined Contributions for the Paris Agreement on Climate change is critical for achieving SDGs. Rise in population, growing unplanned settlements, low rainfall; unsustainable agricultural practices are the primary cause of this wetland decline. This chapter highlights the significance of wetlands, factors responsible for their degradation with major focus on the climate change as one significant factor, and recommendations.

Flood pulse concept

The flood pulse concept addresses the ecotones between rivers and their floodplains. Unlike the lateral riparian influence on stream ecosystem processes where the impact is largely from the landscape to the stream, the flood pulse concept emphasizes the reciprocal exchange between the major river channel and its floodplain. A consequence of this distinction is that the overwhelming bulk of riverine animal biomass derives directly or indirectly from production on the floodplain and not from downstream transport of OM produced higher in the watershed. Although the importance of this aquatic/terrestrial transition zone, the floodplain ecotones, is widely acknowledged, there are few hard data to indicate whether over annual cycles, or longer periods, the primary movement of nutrients and biomass is onto or off the floodplain, or in balance. The general perception of “fertile floodplains” suggests that the periodically inundated floodplains are sinks relative to the river channel. However, the high productivity of adult fish in many floodplain rivers and the concentration of reproductive activity on the floodplain supports the notion that floodplains are sources and the river is a sink, gradually exporting to the sea. At any rate, the seasonal pulsing of river discharge, the flood pulse, is the major force controlling existence, productivity, and interactions of biota in river–floodplain ecosystems.

For any given storm or series of storms, the movement of material and organisms on to the floodplain follows the rising limbs of the hydrographs, and the return to the river channel follows the falling limbs. Unfortunately, application of the flood pulse concept is restricted because of the wide-scale engineering modifications that have isolated rivers from their floodplains. Natural exceptions to the flood pulse concept are rivers flowing through deeply incised canyons.

Abstract

Wetlands can be defined as transitional ecotone ecosystems between terrestrial and aquatic conditions and are characterized by the waterlogged soils. Prevailing anaerobic conditions in wetland soils slow down or suspend decomposition processes of organic matter. These processes are connected with the production of soil biogenic methane (CH4) and carbon dioxide (CO2). CH4 is a product of organic decomposition under anaerobic conditions, while CO2 is a product of organic matter decomposition under aerobic conditions. Anaerobic conditions stabilized in profiles of wetland soils determine a crucial role of wetlands in the carbon cycle at both the local and the global scale. Wetlands sequestrate well carbon into the soil for a long period, and their soils contain about one-third of the global soil carbon stock. It is a bit of a paradox that ecosystems, which are responsible for creating huge carbon storage, are now under scrutiny in case of CH4 emissions into the atmosphere.

1 Introduction

Tidal salt and brackish water marshes are ecotones between land and sea, which occur in the upper intertidal zone of sheltered coastal areas such as estuaries and bays and behind barrier islands. Their hydrology is characterized by regular or irregular inundation by tidewater and subsequent drainage. Tidal effects produce distinct zonation of the herbaceous vegetation, which is related to frequency, duration, and depth of inundation as well as salinity. In addition, the ebb and flow of tides connects the marsh to the adjacent waterbody, and tides are regarded as an energy subsidy that increases primary productivity (Mendelssohn and Kuhn, 2003) and facilitates the exchange of organic carbon, mineral nutrients, sediments, aquatic organisms, and other material. The emergent vegetation consists of a limited number of salt-tolerant species, most commonly grasses, sedges, or rushes. Plant species diversity decreases as salinity increases.

Tidal marshes are productive ecosystems that serve as nursery grounds and habitat for aquatic organisms (Minello et al., 2003, 2008) and food and habitat for wildlife. In many coastal environments, much of the primary production that occurs in tidal marshes is exported to adjacent waters in the form of detritus, which becomes a part of the estuarine food web providing energy for bacteria, fungi, worms, oysters, crabs, shrimp, fish, etc. Other important functions of tidal marshes include buffering of storm surges, storing floodwater, protecting shorelines from erosion, stabilizing dredged material, dampening the effects of waves, trapping waterborne sediments, nutrient cycling and transformations, serving as reservoirs of nutrients, and storage of organic carbon (Mitsch and Gosselink, 2000). Socioeconomic services to humans include esthetics, ecotourism, and education (Peterson et al., 2008). Ecosystem functions and services that benefit people can be characterized as provisioning, regulating, cultural, and supporting (Millennium Ecosystem Assessment, 2005) (Table 22.1).

Table 22.1. Types of Ecosystem Services Provided by Inland and Coastal Wetlands

It is estimated that tidal marshes and mangroves contribute more than $190,000/ha−1 year−1 of such services (Costanza et al., 2014), especially from their contributions to disturbance regulation, pollution control, and waste detoxification (Costanza et al., 1997). Services such as pollution control and waste detoxification, recreation, and provision of natural habitat and biodiversity (i.e., esthetics) are highly valued by the public and studies show that the value of ecosystem services increases with anthropogenic pressure (i.e., they are more highly valued in urban vs. rural landscapes) (Ghermandi et al., 2010). Created and restored wetlands, in particular, are highly valued for biodiversity enhancement, water quality improvement, and flood control (Ghermandi et al., 2010). For salt marshes, the median cost of such restorations in the developed world is more than $67,000 USD/ha in 2010 dollars (Bayraktarov et al., 2016). This value is comparable to restoring equivalent acreage of oyster reef ($66,000 ha−1), less than restoring seagrass $106,000 ha−1 and coral reef (nearly $2 million USD ha) but more relative to mangrove restoration ($39,000 ha−1) (Bayraktarov et al., 2016). However, such costs associated with tidal marsh restoration are less than the value of the benefits they provide.

The area occupied by coastal marshes has been reduced over time, and existing marshes have been degraded because of human activities and natural processes. Anthropogenic sources of marsh loss include dredging, filling, dike and levee construction, drainage, urban and agricultural development, oil and gas exploration, and construction of port facilities, highways, bridges, and airports. Natural forces such as sea level rise, land subsidence, and erosion also result in losses of tidal marshes. Marsh functions and values may be lost because of pollutants such as oil or chemical spills.

The vulnerability of tidal marshes to anthropogenic and natural destruction and degradation has led to an interest in creation of new marshes to replace their lost ecosystem services. In many cases, tidal marsh creation is required by regulatory agencies to mitigate losses resulting from development activities.

13.5.1 Investigating Loops and Feedback Mechanisms in Polyextreme Environments

Mars’ ability to preserve subaerial habitats, ecotones, connectivity networks, and microbial dispersal pathways over time would have depended on fluctuating interactions between multiple environmental extremes and their relative dominance at any given time (Cabrol, 2018). This relative dominance would have impacted the interactions between life and environment and the spatiotemporal nature (e.g., distribution, type, biochemistry, geochemistry, and mineralogy) of biosignatures.

Relative dominance must be thus characterized over geologic timescales and with changing obliquities, including along a depth gradient. This can be accomplished by (a) conducting lab experiments and fieldwork in extreme environments that combine multiple extreme factors relevant to Mars. Emphasizing the characterization of their interactions and their effects on prebiotic, biological processes, and microbial habitats should be prioritized; (b) developing libraries of biogeosignatures resulting from these interactions (e.g., spectral, morphological, metabolic, and genomic). These libraries should be generated at integrated scales from orbit to ground to lab; (c) characterizing biosignature formation through the lens of polyextreme environmental factors and their role on local scale microclimates, including the characterization of microbial habitats (e.g., geology, morphology, mineralogy, sediment texture, structure, and composition) and their preservation potential; and (d) developing theoretical modeling using datasets from past and present missions to support the quantitative and qualitative characterization of the spatiotemporal evolution of polyextreme interactions on Mars, including through episodic changes in obliquity. This characterization should include present-day Mars, which reflects 3.5 billion years of environmental history.

What Happens When Flow is No Longer Unidirectional?

As rivers run toward the sea they encounter an ecotone between river and estuary. Even before salt affects a river, astronomical ocean tides alter flow velocity and direction along rivers for hundreds of kilometers. River flow regimes upstream of large lakes are similarly affected by wind seiches that can reverse hydraulic head gradients (Herdendorf, 1990). All of the bio-hydro-geomorphic controls on stream channel processes discussed in this chapter still apply within this tidal freshwater ecotone with the addition of a long-term, continuous change in flow regime caused by tides. Tidal freshwater zones are being created on decadal time scales as sea level rise forces tides to propagate upstream into previously nontidal environments; the rate at which this nontidal to tidal conversion occurs will increase as sea level rise accelerates.

Tidal freshwater rivers pose a unique challenge for fluvial geomorphology and consequently stream ecology: how do the fluvial patterns and processes discussed throughout this chapter change when river flow becomes bi-directional? Consider the Lane-Borland conceptual model we presented at the beginning of this chapter (Fig. 1). Instead of a single bucket of water hanging on the right arm of the balance, tidal freshwater rivers have two: one for watershed discharge, and a second for the reverse discharge due to tide. This disturbance of a control variable (Fig. 3) induces a response in channel morphology that includes an increase in width and depth (Leopold et al., 1964), although the reaction and relaxation times for these changes are not well understood. These morphological adjustments to tidal flow are ultimately the result of changes in sediment transport.

Sediment moves downstream and upstream within the tidal freshwater zone over the course of a daily tidal cycle. Over timescales of weeks to months, the net direction of suspended sediment (Guézennec et al., 1999) and bedload (Ashley, 1980) transport can even be directed upstream toward the watershed. Net landward sediment flux is driven by higher velocity flow during the flood (upstream-directed) portion of the tidal cycle than the ebb portion (downstream-directed) (Yankovsky et al., 2012; Ensign et al., 2013). This process is so persistent that it can even move marine sediments upstream into freshwater (Schuchardt and Schirmer, 1990). Bi-directional sediment flux affects channel morphology and riparian wetlands, but sediment delivery to riparian wetlands is particularly important because they exist at sea level. Without a sediment supply capable of maintaining a vertical rate of accretion at least equal to sea level rise, these wetlands are inundated and the river channel widens. This is the case in the southeastern United States. where low sediment supply to tidal freshwater riparian forests is too slow to keep pace with sea level rise (Ensign et al., 2014a), subsequently affecting vegetation, hydroperiod, channel width, flow regime, and sediment transport (Conner et al., 2007 and references therein; Barendregt et al., 2009 and references therein).

This cascade of geomorphic impacts caused by tides ultimately affects ecosystem production due to light availability (Table 3). As riparian wetlands are inundated, the increased channel width enhances phytoplankton growth (Ensign et al., 2012). In larger tidal freshwater rivers, increased residence time and decreased depth facilitates phytoplankton growth (Bukaveckas et al., 2011). Zooplankton (Ensign et al., 2014b) and bivalve filter feeders (Strayer et al., 2008) flourish on this productivity and fuel consumption to higher trophic levels. This highly productive tidal freshwater zone warrants management of freshwater inflow using environmental flows (Table 5), yet with tides forcing overbank flow to occur on a daily basis, watershed discharge is not the major variable affecting in-stream habitat (the types of in-stream habitats within the coastal plain also differ considerably from those of piedmont rivers described earlier in this chapter). The divorce of river stage from river discharge poses new and exciting challenges for fluvial geomorphology and stream ecology.

We framed this discussion of tidal freshwater rivers as a challenge to our basic understanding of fluvial processes and how it changes with bi-directional flow. While an invigorated research program on this phenomenon will advance aquatic sciences, it will also yield basic knowledge needed for effective environmental management in a changing climate with accelerating sea level rise. Some urgent questions include: where along the tidal gradient of a river does the magnitude and frequency of watershed runoff during storms become swamped by tides? How does this position change with river size? How does the rate of sea level rise affect the reaction and relaxation times of geomorphic and ecological systems in the tidal freshwater zone? River scientists, aided by estuarine geomorphologists, need to build on the foundation of fluvial processes presented in this chapter to find the answers.

Community Transition Patterns

Typically, the overlap between two adjacent habitats (ecotones) forms a particularly species-rich community (Lomolino et al., 2010). In contrast, the transition zone between the Afromontane and the Afroalpine is not characterized by an enhanced number of bird taxa. This finding has an interesting parallel in terrestrial invertebrate groups (e.g., Carabid beetles) which also do not constitute a separate community above the Ericaceous belt on Mt. Kilimanjaro but an impoverished set of montane communities (Franz, 1979). However, this similarity should not be overly generalized since beetles on Mt. Kenya and in the Ethiopian highlands do appear to form specific alpine communities (Franz, 1979). Moreover, soil invertebrates and even small mammals are much less mobile and often more specifically bound to local ecological conditions than birds. The huge species diversity of shrews on isolated African mountaintops is an example of such regional diversification as a result of adaptive radiations (e.g., Stanley et al., 2015; Lavrenchenko et al., 2016). In contrast, the mobility of birds combined with their ability to quickly avoid unfavorable conditions, may have prevented them from forming distinct Afroalpine communities.

Additionally, the temporal patterns of presence and absence of Afroalpine birds are not well understood and the potential effect and extent of elevational migration in the Afroalpine has scarcely been studied. In particular, members of groups 2 and 3 may perform temporal elevational migrations, thus shifting their ranges between the Afroalpine and the Afromontane, either regularly or opportunistically. Such movements have been found in Afromontane birds (Brown et al., 1982) and are likely to take place in some Afroalpine taxa as well. For instance, there is evidence that at least some species of the Ethiopian alpine zones (e.g., Blue-winged Goose or Spot-breasted Plover) apparently leave these habitats, possibly following the availability of food or water (personal observation), while their whereabouts outside their well-documented highland occurrences are virtually unknown. Moreover, at least for the White-collared Pigeon a daily movement between high-elevation foraging sites and much lower roosting sites has been described (Boswall and Demment, 1970) but such patterns of movement are insufficiently known for other Afroalpine birds.

Another aspect of particular ecological interest is the close dependency of raptors on small mammal communities in the Ethiopian Bale Mountains. The exceptional species richness and abundance of small mammals in this area sustains a likewise unusually speciose raptor community that opportunistically exploits this food resource (Colwell et al., 2008). This might explain why there are so many raptors found among group 4.

The numerical difference between the Ethiopian and East African Afroalpine bird taxa differs from the finding of Moreau (1966), who already suspected his assessment to be biased because of the then less well-known Ethiopian avifauna. Although the situation has since changed, the biological information thus far collected remains comparatively poor and requires further focused study.