Les difficultes de developpement de l'Ecotourisme dans les aires protegées du Cameroun

La création du premier parc national mondial le 1er mars 1872 à Yellowstone aux Etats-Unis, suivie 26 ans plus tard par celle de la Sabie Game Reserve qui devint le Krüger National Park em Afrique du Sud, a ouvert la voie à la multiplication des aires protégées dans le monde entier. Le but de celles-ci est de preserver le potentiel naturel des différents pays et de promouvoir le développement durable par l’écotourisme. Cependant, le Cameroun a attendu 60 ans pour créer sa première réserve (1932) érigée 36 ans plus tard (1968) en parc national (le Parc de Waza). A ce jour, ce pays compte près de 77 zones protégées d’une superfície totale de 7,51 millions d’hectares, soit plus de 15% du territoire national. Dans l’ensemble, on dénombre 12 parcs et reserves de plus de 2,3 millions d’ha de superficie. Mais ceux-ci n’ont de parcs que de nom: en effet, ils bénéficient d’une attention faible de la part des services publics compétents. De plus, ceux qui sont en charge de la promotion de l’industrie touristique sont insuffisamment outillés ou qualifiés. Cet article vise à établir um diagnostic critique des principales difficultés du développement de l’écotourisme au Cameroun dans les aires protégées.

LOAC: a small aerosol optical counter/sizer for ground-based and balloon measurements of the size distribution and nature of atmospheric particles – Part 1: Principle of measurements and instrument evaluation

International audienceThe study of aerosols in the troposphere and in the stratosphere is of major importance both for climate and air quality studies. Among the numerous instruments available, optical aerosol particles counters (OPCs) provide the size distribution in diameter range from about 100 nm to a few tens of µm. Most of them are very sensitive to the nature of aerosols, and this can result in significant biases in the retrieved size distribution. We describe here a new versatile optical particle/sizer counter named LOAC (Light Optical Aerosol Counter), which is light and compact enough to perform measurements not only at the surface but under all kinds of balloons in the troposphere and in the stratosphere. LOAC is an original OPC performing observations at two scattering angles. The first one is around 12°, and is almost insensitive to the refractive index of the particles; the second one is around 60° and is strongly sensitive to the refractive index of the particles. By combining measurement at the two angles, it is possible to retrieve the size distribution between 0.2 and 100 µm and to estimate the nature of the dominant particles (droplets, carbonaceous, salts and mineral particles) when the aerosol is relatively homogeneous. This typology is based on calibration charts obtained in the laboratory. The uncertainty for total concentrations measurements is ±20% when concentrations are higher than 1 particle cm-3 (for a 10 min integration time). For lower concentrations, the uncertainty is up to about ±60% for concentrations smaller than 10-2 particle cm-3. Also, the uncertainties in size calibration are ±0.025 μm for particles smaller than 0.6 μm, 5% for particles in the 0.7-2 μm range, and 10% for particles greater than 2 μm. The measurement accuracy of submicronic particles could be reduced in a strongly turbid case when concentration of particles > 3 µm exceeds a few particles cm-3. Several campaigns of cross-comparison of LOAC with other particle counting instruments and remote sensing photometers have been conducted to validate both the size distribution derived by LOAC and the retrieved particle number density. The typology of the aerosols has been validated in well-defined conditions including urban pollution, desert dust episodes, sea spray, fog, and cloud. Comparison with reference aerosol mass monitoring instruments also shows that the LOAC measurements can be successfully converted to mass concentrations

LOAC: a small aerosol optical counter/sizer for ground-based and balloon measurements of the size distribution and nature of atmospheric particles – Part 2: First results from balloon and unmanned aerial vehicle flights

International audienceIn the companion (Part I) paper, we have described and evaluated a new versatile optical particle counter/sizer named LOAC (Light Optical Aerosol Counter), based on scattering measurements at angles of 12 and 60 •. That allows for some typology identification of particles (droplets, carbonaceous, salts, and mineral dust) in addition to size-segregated counting in a large diameter range from 0.2 µm up to possibly more than 100 µm depending on sampling conditions (Renard et al., 2016). Its capabilities overpass those of preceding optical particle counters (OPCs) allowing the characterization of all kind of aerosols from submicronic-sized absorbing carbonaceous particles in polluted air to very coarse particles (> 10–20 µm in diameter) in desert dust plumes or fog and clouds. LOAC's light and compact design allows measurements under all kinds of balloons , on-board unmanned aerial vehicles (UAVs) and at Published by Copernicus Publications on behalf of the European Geosciences Union. 3674 J.-B. Renard et al.: LOAC: a counter/sizer for ground-based and balloon measurements – Part 2 ground level. We illustrate here the first LOAC airborne results obtained from a UAV and a variety of scientific balloons. The UAV was deployed in a peri-urban environment near Bordeaux in France. Balloon operations include (i) tethered balloons deployed in urban environments in Vi-enna (Austria) and Paris (France), (ii) pressurized balloons drifting in the lower troposphere over the western Mediter-ranean (during the Chemistry-Aerosol Mediterranean Experiment – ChArMEx campaigns), (iii) meteorological sounding balloons launched in the western Mediterranean region (ChArMEx) and from Aire-sur-l'Adour in southwestern France (VOLTAIRE-LOAC campaign). More focus is put on measurements performed in the Mediterranean during (ChArMEx) and especially during African dust transport events to illustrate the original capability of balloon-borne LOAC to monitor in situ coarse mineral dust particles. In particular, LOAC has detected unexpected large particles in desert sand plumes