1. Introduction
Sacred groves, also known as church forests, fetish forests and sacred forests, are found all over the world including Ethiopia, Japan, Morocco, India, and Ghana [
1,
2,
3]. These sites are often seats of religious and cultural ritual that have been maintained through community conservation and are refugia of biodiversity; in fact, there is a significant network of large “shadow” conservation sites that are protected because of their sacredness [
4]. Recent work shows that many rare and endemic species are found only in sacred groves [
4]. In turn, these forests provide essential ecosystem services that include both the material provisions (timber and non-timber forest products), non-material (spiritual value, cultural value), and support services (nutrient cycling, water storage, carbon storage, pollination) [
5,
6]. Globally, sacred natural sites are threatened by population growth, social inequity, poor or no governance, political corruption and government policies that encourage unsustainable land use practices [
4].
In the Amhara region of northern Ethiopia, centuries of deforestation likely driven by the need for fuel and agricultural and grazing land has resulted in radical alteration of the natural Ethiopian landscape [
7] (
Figure 1). Yet even as deforestation has ravished the landscape, sacred sites have demonstrated remarkable resilience in the face of change. While the exact number is unknown, thousands of these church forests currently exist as islands in a sea of degraded land (
Figure 2a) where they have become centers of forest conservation. Such forests also provide human services as they are the location of the Ethiopian Orthodox Tewahido Church (EOTC) in which an Orthodox priest, his monks and disciples live and maintain the church at it’s center [
2]. Local followers (men, women and children) pray in the church and use the forest ecosystems for firewood, honey, freshwater and cattle grazing [
8].
Figure 1.
Location of study sites and sacred grove density across study region, Ethiopia.
Figure 1.
Location of study sites and sacred grove density across study region, Ethiopia.
Figure 2.
(a) GoogleEarth image of study site Debresena (lower right) and other sacred groves. Arrows point to forest. (b) GoogleEarth image of one study forest, Debresena. The round Building in the center of the grove is the church.
Figure 2.
(a) GoogleEarth image of study site Debresena (lower right) and other sacred groves. Arrows point to forest. (b) GoogleEarth image of one study forest, Debresena. The round Building in the center of the grove is the church.
Deforestation, and land-use change in general, is one of the most serious threats to biodiversity and ecosystem function [
9,
10]. In tropical regions, in particular, deforestation has reduced extant forest globally by 50% over the last 200 years [
11]. This forest change has impacts at multiple scales including local and regional weather patterns, carbon storage, biodiversity, and other ecosystem services [
9,
12,
13,
14]. The drivers of forest degradation by which we mean disturbances that range from deforestation to those that do not involve forest clearing, such as selective logging, harvesting of non-timber forest products, and cattle grazing—are largely linked to economically driven human activity [
15]. Most notably, land degradation and clearing in tropical regions has been associated with population growth, road establishment, non-timber forest product harvesting, timber harvesting, fuel, grazing land establishment, and cultivation of oil palm and soybeans [
15].
Assessing forest degradation and land-use change over time is critical in conservation efforts to assess overall ecosystem status which can be done using basic landscape-scale inventory data (e.g., number of sacred groves, total area of forest) [
16]. However, inventory information regarding the present status of the sacred grove mosaic in Ethiopia is lacking. Reports on sacred grove number vary from 1404 in the South Gondar Administrative Zone (SDAZ) alone to as many as 35,000 sacred groves in the vicinity of Lake Tana and the northern highlands [
17]. Beyond basic inventory data, in highly fragmented landscapes similar to northern Ethiopia, the distance between forest patches and the number of patches per unit area are also important determinates of both forest health and resilience. Measures of isolation, such as the distance to each forest’s nearest neighbor has been established as useful information in regards to regeneration capacity [
18,
19]. Lehouk [
20], for example, demonstrated that forest patch isolation was critically important in the context of fruiting plant regeneration in the afromontane forests of Kenya. Isolation measures were also found to relate to species richness in the afromontane forests of South Africa [
21].
Measures of forest shape can be an effective way to infer “edge” effects—changes to forest character due to climatic changes moving from the edge to the interior, with the “edge” of the forest having greater light intensity, lower soil moisture, and increased wind effect. Such edge effects are known to degrade forests and can be felt up to 500 m into their interior [
22]. Edge effects also impact soil and foliar nutrient status. The edge potentially receives more N deposition [
23] which could translate to greater N status in both plant leaves and soils. In contrast, litter decay rates may decrease along the edge because of decreased soil moisture which feedbacks on decreased soil and foliar nutrient status. Plants that experience greater water stress, as seen in edges, exhibit greater water use efficiency in their enriched δ
13C signals compared to non-edge plants [
24]. Thus forest size is a large determinant of forest resilience, with smaller patches having a greater edge and thus more vulnerable to degradation [
25]. In forest fragments in Brazil, small fragments (1–10 ha) had greater tree mortality than large fragments (100 ha) [
26] and animal richness and abundance also declined, as did ecosystem services [
27], with forest size. These edge effects and isolation can impact regeneration due to lack of seed sources [
18]. In the sacred groves of Ethiopia in particular, soil compaction from livestock grazing which reduces seedling establishment [
28,
29]. In addition to aboveground impacts on forest structure and function, shifts from a forested landscape to grazing land can have differential effects on soil status. Cattle grazing increases soil compaction (measured as bulk density, g cm
−3) which reduces air pockets and deters seedling germination and root depth [
30]. Furthermore, with tree harvest followed by stable, undeviating grazing system, forest regeneration is hindered [
28]. Studies by Murty
et al. [
31] showed a decrease in C and N in forest soil
versus cultivated land soil with an average loss of about 24% and 15% respectively. The change in nutrient composition was afforded to changes in the quantity and quality of organic C inputs to the soil, nutrient inputs and deficits, and intensification of decomposition through soil disruption—all factors that can reduce forest regeneration. In contrast, many studies, have found the increases in C and N stocks with forest conversion likely due to land-use history [
32]. Quantifying the extent of the edge effects and forest clearing on soil status and properties in and around small, vulnerable sacred groves can inform regeneration efforts in the region.
Increased drought exacerbated by climate change, and human population growth is putting more pressure on Ethiopian sacred groves [
29]. In order to assess the status of sacred groves in the Amhara Region of Ethiopia we performed a two-scale analysis of sacred groves: (1) patterns of distribution and shape at the regional scale and; (2) nutrient status at the local scale with particular focus on soil status. At a regional scale we inventoried and analyzed the spatial pattern of sacred groves on the landscape. We hypothesized that larger forest fragments would have greater crown closure and shape complexity. At the local scale we analyzed the soil and foliar nutrient status of two small fragments that varied with elevation as representative of small groves in the region. We hypothesized that soil status, as measured by total C, N and C:N ratio would decrease with greater degradation (interior-edge-clearing) and that foliar nutrient status would similarly be higher in the interior than edge. Understanding forest status at both the regional and local scales allows us to develop a more complete view of the extent of forest degradation in the region.