Paul Laris

Burning the Seasonal Mosaic: Preventative Burning Strategies in the Wooded Savanna of Southern Mali

Data are presented indicating a seasonal mosaic pattern of burning in the savanna of southern Mali. A seasonal mosaic is a landscape that is annually re-created by people, and which contains patches of unburned, early burned, and recently burned vegetation. A survey of over 100 farmers and in-depth interviews demonstrates that rural inhabitants of southern Mali begin an annual burning regime early in the dry season in order to fragment the landscape, with the goal of preventing later fires that can damage natural resources. The process of gradually burning off the driest vegetation creates a seasonal mosaic of habitat patches that increases the potential of the landscape for a variety of dry season land uses, including hunting, gathering of savanna products, and grazing. An analysis of a series of Landsat images shows that the practice of mosaic burning is widespread in the wooded savanna, in which burning usually begins early and large fires are rare. On the basis of recent developments in ecological theory and empirical evidence from similar burning regimes in parts of Australia, it is suggested that seasonal mosaic burning in Mali not only prevents damaging late-season fires but increases biodiversity. It is concluded that discourse on African savanna burning overemphasizes the ecologically detrimental aspects of fire, while neglecting the beneficial ones resulting in misguided policies that pose a threat to human livelihoods and savanna ecosystems.

Humanizing Savanna Biogeography: Linking Human Practices with Ecological Patterns in a Frequently Burned Savanna of Southern Mali

The savanna biome is defined by the codominance of grasses and trees, the precise ratio of which is a function of numerous variables, both natural and anthropogenic. Fire is a critical determinant of the tree-to-grass ratio because it can suppress tree establishment and growth. Despite the fact that nearly all fires have human causes, most savanna fire ecology models are based solely on ecological variables and fail to integrate human land and fire use patterns. To understand how human burning practices, land cover patterns, and fire regimes are linked I combined the results of an image-based burn scar analysis and land cover maps generated from a Landsat database covering thirty years with interview and survey results. I documented the spatially explicit fire regime for an area of Sudan savanna in southern Mali and linked it to human practices and land cover patterns. The study concludes that burning creates a seasonal mosaic in which some patches regularly burn early and others late, whereas some areas rarely if ever burn. Ecologists attribute mosaic fire regimes to natural factors such as plant succession, but this research demonstrates that the regime is a function of the combined effects of edaphic conditions, vegetation patterns, land use, and widespread burning practices. The anthropogenic burning regime documented here differs from the one based on ecological theory in that its spatiotemporal pattern is relatively consistent from year to year. The findings demonstrate the need to “humanize” savanna models by breaking nature–society dichotomies and synthesizing natural and social science explanations.

Fire ecology and fire politics in Mali and Madagascar

Anthropogenic fires dominate Africa, where they have long shaped landscapes and livelihoods. Humans evolved in Africa’s fire-prone grasslands and savannas, eventually taking ignition into their own hands. This chapter reviews current knowledge about and concerns over lire in two African countries. Mali and Madagascar. Vast areas of land burn in both countries each year as people light fires to shape vegetation communities for a number of often overlapping and sometimes competing reasons, ranging from pasture and game management, to crop field preparation, to pest and wildfire control. In Mali, hunting and agropastoral fires shape vegetation zones along the gradient between the dry north and the more humid south. Their anthropogenic nature removes much of the interannual variation common in fire regimes elsewhere—they are a regular, predictable feature of the landscape. In Madagascar, fires prepare and maintain the vast pastures of the interior, and enable farmers to cultivate farther into the few remaining stands of forest. Although rural populations rely upon fire for numerous livelihood activities, they sometimes struggle to control fire. Policy makers have long criticized the fires for reducing tree cover and contributing to land degradation, raising the specter of desertification in Mali and deforestation in Madagascar. As a result, colonial and independent governments have periodically tried to eradicate—or at least minimize—landscape burning. These efforts wax and wane with the political context, with drought cycles, and with periods of international concern. Government fire restrictions are frequently perceived by rural residents as an imposition on their way of life, and enforcement has led to animosity against government agents. Given people’s resistance, as well as fire’s inevitability in wet-dry grassy landscapes, fire management is largely at a standstill. Some form of co-management is likely the only viable solution, yet in order for this to work, governments will have to accept the usefulness and inevitability of many fires.

The Human Ecology and Geography of Burning in an Unstable Savanna Environment

Abstract According to new ecological theories, many savannas are inherently in disequilibrium and can flip from tree-dominated to grass-dominated landscapes depending upon the disturbance regime. In particular, a shift in a fire regime to a more frequent and intensive one can radically alter the tree-to-grass ratio in a given savanna. Drawing upon the ecological buffering model we argue that savanna persistence requires a relatively stable fire regime. We hypothesize that anthropogenic burning practices perform this function by producing a regular annual spatiotemporal pattern of fire that is linked to vegetation type. We test this hypothesis using a study of two areas, one in Mali and the other Burkina Faso. We use two sources of satellite data to produce an 11-year time series of the spatiotemporal pattern of fires and an example of the annual burned area pattern these fires produce. We combine the analysis of satellite imagery with interviews of rural inhabitants who set fires to understand the logic underlying the patterns of fire. Analysis of a time series of imagery reveals a strikingly regular annual spatiotemporal pattern of burning for both study areas, which cannot be explained by the regional climatic pattern alone. We conclude that the regularity of the annual fire regime in West Africa is a human-ecological phenomenon closely linked to vegetation type and controlled by peoples burning practices. We argue that the anthropogenic burning regime serves to buffer the savanna and maintain its ecological stability.

HOBBY RANCHING AND CHILE'S LAND‐REFORM LEGACY*

ABSTRACT. Twentieth‐century land reform in Chile reflects familiar themes. The state subdivided large land monopolies, ostensibly for social justice reasons: to provide opportunities for campesinos to earn a living from agriculture. In southern Chiles Tierra del Fuego a combination of social justice, nationalism, and geopolitical concerns stimulated land reform between 1924 and 1978. The effort succeeded in creating a new material landscape oriented around smaller ranches but failed to meet its socioeconomic goals. In a scenario that resonates with reforms elsewhere in Latin America, an elitist cultural landscape dominated by large‐holding corporations was replaced with another elitist landscape, though in a different form. Politically well‐connected and essentially absentee landholders acquired subdivided land and began to practice “hobby ranching.” The history of land reform in Tierra del Fuego demonstrates how new socioeconomic conditions created over the course of many decades have left their imprint on land use and the biophysical landscape. It also contributes to larger regional debates about the role of land degradation in stocking‐rate decline.

West African environmental narratives and development-volunteer praxis

ABSTRACT. Environmental narratives in Africa have been examined in a flurry of publications since the mid‐1990s. In this article we seek to offer insights into the role and motivations of volunteer development workers in perpetuating environmental narratives. We examine the factors that led to the questioning or nonquestioning of environment‐development discourses and their influence, if any, on the actual work undertaken by volunteers. As former development volunteers, we also explore the role that the development‐volunteer experience subsequently played in shaping our own research as academics. Our analysis is based largely on our tenure as U.S. Peace Corps volunteers in Mali from 1987 until 1989 and our later experiences as academics. We draw on our memories, interviews with former colleagues, and training materials to describe how volunteers were introduced to, and encouraged to act on, environmental problems in the West African Sudano‐Sahel. We adopt a reflexive approach to explore briefly how our experiences as volunteers influenced our research and writing as academics.

Humanizing savanna models: integrating natural factors and anthropogenic disturbance regimes to determine tree–grass dynamics in savannas

Explaining co-dominance of grasses and trees in savannas has confounded ecologists and biogeographers for decades. One reason is the complex nature of savanna human ecology; co-dominance can be caused by edaphic conditions, biotic factors, and/or human practices. New models consider savannas to be in disequilibrium and emphasize tree life histories, recognizing that events create opportunities for tree establishment. While much emphasis has been placed on how disturbances such as fire suppress trees, there has been less focus on how multiple disturbances interact to alter tree establishment. This study examines the impacts of hoe-farming, grazing, and burning on tree establishment and growth. It combines results from a 4-year field experiment with those from a long-term natural experiment. The study finds that the subtle changes in soil compaction and permeability as well as grass cover that result from hoe-farming counter the negative effects of fire on tree establishment and growth, especially on clay soils.

The early/late fire dichotomy Time for a reassessment of Aubréville’s savanna fire experiments

A fundamental principal of savanna fire ecology is that the fire regime determines vegetation cover, especially as it pertains to trees. A corollary is that late fires are more damaging to trees than early fires. Much evidence in support of this principle has been derived from a series of long-term burning experiments based on the pioneering work of André Aubréville. Eighty years ago, Aubréville devised an experiment to study the impacts of fire on savanna trees in Africa. The design conventions of this study remain highly influential. It is now clear, however, that the dates chosen by Aubréville and his followers do not reflect the burning practices of West African people. Dates that were chosen for “early” and “late” are not representative of actual fire timing; they represent extremes. This study has four goals: (i) to critically review the results of the burning experiments; (ii) to examine them in the context of results from recent savanna fire studies; (iii) to evaluate their limitations based on data for actual burning practices and fires from West Africa; and (iv) to critically evaluate the use of the early/late terminology in contemporary fire research. We find the majority of West African fires occur during the “middle” of the fire season. Our field studies find that fire temperature and burn completeness are highest in the middle-season. We conclude that the early/late fire dichotomy is not sufficient for understanding the impacts of anthropogenic fires in the region and we make suggestions for rethinking its use more broadly.

Buffering the savanna: fire regimes and disequilibrium ecology in West Africa

According to contemporary ecological theory, the mechanisms governing tree cover in savannas vary by precipitation level. In tropical areas with mesic rainfall levels, savannas are unstable systems in which disturbances, such as fire, determine the ratio of trees to grasses. Precipitation in these so-called “disturbance-driven savannas” is sufficient to support forest but frequent disturbances prevent transition to a closed canopy state. Building on a savanna buffering model we argue that a consistent fire regime is required to maintain savannas in mesic areas. We hypothesize that the spatiotemporal pattern of fires is highly regular and stable in these areas. Furthermore, because tree growth rates in savannas are a function of precipitation, we hypothesize that savannas with the highest rainfall levels will have the most consistent fire pattern and the most intense fires—thus the strongest buffering mechanisms. We analyzed the spatiotemporal pattern of burning over 11 years for a large subset of the West African savanna using a moderate resolution imaging spectroradiometer active fire product to document the fire regime for three savanna belts with different precipitation levels. We used LISA analysis to quantify the spatiotemporal patterns of fires, coefficient of variance to quantify differences in peak fire dates, and center or gravity pathways to characterize the spatiotemporal patterns of the fires for each area. Our analysis confirms that spatiotemporal regularity of the fire regime is greater for mesic areas that for areas where precipitation is lower and that areas with more precipitation have more regular fire regimes.

Comparing the Long-Term Impacts of Different Anthropogenic Disturbance Regimes on California Sage Scrub Recovery

California sage scrub (CSS) is a highly threatened vegetation community in coastal Southern California, 90 percent of which has been lost. Understanding CSS recovery is critical to its survival. This study compares long-term effects of grazing, cultivation, and mechanical disturbance in Southern California by tracking the extent of exotic grassland in two valleys in the Santa Monica Mountains over sixty years using aerial image analysis. Native shrubs returned to the grazed valley over one and one-half times faster than they did in the cultivated valley. Cultivation might result in a type conversion of CSS to exotic annual grassland that resembles a new steady state.